JP7359168B2 - Magnetic recording media, magnetic recording/reproducing devices, and magnetic recording media cartridges - Google Patents

Description

The present disclosure relates to a magnetic recording medium, a magnetic recording/reproducing device using the same, and a magnetic recording medium cartridge.

Tape-shaped magnetic recording media having a magnetic layer are widely used for storing electronic data. A data band including a plurality of recording tracks is provided in a magnetic layer of a magnetic recording medium, and data is recorded on this recording track. Further, a servo band is provided in the magnetic layer at a position adjacent to the data band in the width direction, and a servo signal is recorded in this servo band. The magnetic head is aligned with the recording track by reading the servo signal recorded on the servo band.

There are two methods for recording data on magnetic recording media: horizontal magnetic recording, which records data by horizontally magnetizing magnetic particles in a magnetic layer, and horizontal magnetic recording, which records data by magnetizing magnetic particles in a magnetic layer in a perpendicular direction. A perpendicular magnetic recording method is known. In general, perpendicular magnetic recording can record data at a higher density than horizontal magnetic recording. The present applicant has disclosed a technique for obtaining a reproduced waveform of a servo signal having good symmetry when the magnetization direction of the servo signal includes a component in the vertical direction (see, for example, Patent Document 1).

Japanese Patent Application Publication No. 2014-199706

In recent years, as the amount of data to be recorded has increased, there has been a demand for higher density recording. A tape-shaped magnetic recording medium is housed in, for example, a magnetic recording cartridge. In order to further increase the recording capacity per magnetic recording cartridge, the total thickness of the magnetic recording medium housed in the magnetic recording cartridge is made thinner, and the length of the magnetic recording medium per magnetic recording cartridge (so-called tape length) is reduced. ) may be considered. However, magnetic recording media with a thin overall thickness may have poor running stability. In particular, when repeatedly recording and/or reproducing, a magnetic recording medium having a thin overall thickness may change its surface condition (particularly the surface condition related to friction) and deteriorate running stability. Therefore, there is a need for a magnetic recording medium that can achieve even higher density recording while maintaining running stability.

A magnetic recording medium according to an embodiment of the present disclosure is a tape-shaped magnetic recording medium, and includes a base body containing polyester as a main component, and a plurality of magnetic powders provided on the base body, on which data signals can be recorded. with a possible magnetic layer. The average thickness of the magnetic recording medium is 5.6 μm or less, the average thickness of the substrate is 4.2 μm or less, and the average thickness of the magnetic layer is 90 nm or less. The average aspect ratio of the magnetic powder is 1.0 or more and 3.0 or less. The coercive force of the magnetic recording medium in the perpendicular direction is 3000 Oe or less. The ratio of the coercive force in the longitudinal direction of the magnetic recording medium to the coercive force in the vertical direction of the magnetic recording medium is 0.8 or less. The magnetic layer contains a lubricant. Furthermore, the entire BET specific surface area of the magnetic recording medium in a state where the lubricant is removed is 2.5 m ² /g or more.

A magnetic recording and reproducing apparatus as an embodiment of the present disclosure includes a feeding section that can sequentially feed out the above-described magnetic recording medium, a winding section that can wind up the magnetic recording medium sent out from the feeding section, The magnetic head is provided with a magnetic head capable of writing information to the magnetic recording medium and reading information from the magnetic recording medium while being in contact with the magnetic recording medium traveling from the sending section to the winding section.

A magnetic recording medium cartridge as an embodiment of the present disclosure includes the above-described magnetic recording medium and a casing that houses the magnetic recording medium.

A magnetic recording medium, a magnetic recording/reproducing device, and a magnetic recording medium cartridge according to an embodiment of the present disclosure have the above-described configuration, which is advantageous for high-density recording of data while maintaining good running stability. It is.

1 is a cross-sectional view of a magnetic recording medium according to an embodiment of the present disclosure. 2 is a cross-sectional view schematically showing the cross-sectional structure of ε iron oxide particles contained in the magnetic layer shown in FIG. 1. FIG. 2 is a graph showing an example of an SFD curve of the magnetic recording medium shown in FIG. 1. FIG. 2 is a schematic explanatory diagram showing the layout of data bands and servo bands in the magnetic recording medium shown in FIG. 1. FIG. 5 is a schematic explanatory diagram showing an enlarged view of the data band shown in FIG. 4. FIG. FIG. 5 is a schematic explanatory diagram showing an enlarged servo signal recording pattern in the servo band shown in FIG. 4; It is a schematic diagram explaining the measuring method of a dynamic friction coefficient. 2 is a schematic diagram of a recording/reproducing apparatus using the magnetic recording medium shown in FIG. 1. FIG. FIG. 7 is a cross-sectional view schematically showing a cross-sectional structure of epsilon iron oxide particles as a modified example.

Embodiments of the present disclosure will be described in detail below with reference to the drawings. Note that the explanation will be given in the following order.
1. One embodiment 1-1. Configuration of magnetic recording medium 1-2. Manufacturing method of magnetic recording medium 1-3. Configuration of recording/reproducing device 1-4. Effect 2. Variant

<1. One embodiment>
[1-1 Configuration of magnetic recording medium 10]
FIG. 1 shows an example of a cross-sectional configuration of a magnetic recording medium 10 according to an embodiment of the present disclosure. As shown in FIG. 1, the magnetic recording medium 10 has a laminated structure in which a plurality of layers are laminated. Specifically, the magnetic recording medium 10 includes a long tape-shaped base 11, a base layer 12 provided on one main surface 11A of the base 11, and a magnetic layer provided on the base layer 12. 13, and a back layer 14 provided on the other main surface 11B of the base 11. The surface 13S of the magnetic layer 13 becomes the surface on which the magnetic head comes into contact and travels. Note that the base layer 12 and the back layer 14 are provided as necessary, and may be omitted. Note that the average thickness of the magnetic recording medium 10 is preferably 5.6 μm or less, for example.

The magnetic recording medium 10 has a long tape shape, and travels along its longitudinal direction during recording and reproducing operations. It is preferable that the magnetic recording medium 10 is used in a recording/reproducing apparatus that includes a ring-type head as a recording head, for example.

(Base 11)
The base 11 is a nonmagnetic support that supports the underlayer 12 and the magnetic layer 13. The base 11 is in the form of a long film. The upper limit of the average thickness of the base body 11 is preferably 4.2 μm or less, more preferably 4.0 μm or less. When the upper limit of the average thickness of the base body 11 is 4.2 μm or less, the recording capacity that can be recorded in one data cartridge can be increased compared to a general magnetic recording medium. The lower limit of the average thickness of the base body 11 is preferably 3 μm or more, more preferably 3.2 μm or more. When the lower limit of the average thickness of the base body 11 is 3 μm or more, a decrease in strength of the base body 11 can be suppressed.

The average thickness of the base 11 is determined as follows. First, a 1/2 inch wide magnetic recording medium 10 is prepared and cut into a length of 250 mm to produce a sample. Subsequently, the layers of the sample other than the substrate 11, that is, the underlayer 12, the magnetic layer 13, and the back layer 14, are removed using a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, using a laser holo gauge (LGH-110C) manufactured by Mitutoyo as a measuring device, the thickness of the substrate 11, which is a sample, is measured at five or more positions. Thereafter, the average thickness of the base 11 is calculated by simply averaging (arithmetic mean) these measured values. Note that the measurement position is randomly selected from the sample.

The base body 11 contains, for example, polyester as a main component. In addition to polyesters, the base 11 may contain at least one of polyolefins, cellulose derivatives, vinyl resins, and other polymer resins. When the base body 11 contains two or more of the above materials, the two or more materials may be mixed, copolymerized, or laminated.

Examples of the polyesters contained in the base 11 include PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PCT (polycyclohexylene dimethylene terephthalate), and PEB. (polyethylene-p-oxybenzoate) and polyethylene bisphenoxycarboxylate.

The polyolefins contained in the base body 11 include, for example, at least one of PE (polyethylene) and PP (polypropylene). The cellulose derivative includes, for example, at least one of cellulose diacetate, cellulose triacetate, CAB (cellulose acetate butyrate), and CAP (cellulose acetate propionate). The vinyl resin includes, for example, at least one of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).

Other polymeric resins contained in the base 11 include, for example, PA (polyamide, nylon), aromatic PA (aromatic polyamide, aramid), PI (polyimide), aromatic PI (aromatic polyimide), and PAI (polyamideimide). ), aromatic PAI (aromatic polyamideimide), PBO (polybenzoxazole, e.g. Zylon (registered trademark)), polyether, PEK (polyetherketone), polyether ester, PES (polyether sulfone), PEI ( (polyetherimide), PSF (polysulfone), PPS (polyphenylene sulfide), PC (polycarbonate), PAR (polyarylate), and PU (polyurethane).

(Magnetic layer 13)
The magnetic layer 13 is a recording layer for recording signals. The magnetic layer 13 includes, for example, magnetic powder, a binder, and a lubricant. The magnetic layer 13 may further contain additives such as conductive particles, abrasives, and rust preventives, if necessary.

The magnetic layer 13 has a surface 13S provided with a large number of holes. Lubricant is stored in these many holes. Preferably, the large number of holes extend perpendicularly to the surface of the magnetic layer 13. This is because the ability to supply lubricant to the surface 13S of the magnetic layer 13 can be improved. Note that some of the many holes may extend in the vertical direction.

The arithmetic mean roughness Ra of the surface 13S of the magnetic layer 13 is 2.5 nm or less, preferably 2.2 nm or less, and more preferably 1.9 nm or less. When the arithmetic mean roughness Ra is 2.5 nm or less, excellent electromagnetic conversion characteristics can be obtained. The lower limit of the arithmetic mean roughness Ra of the surface 13S of the magnetic layer 13 is preferably 1.0 nm or more, more preferably 1.2 nm or more, and even more preferably 1.4 nm or more. When the lower limit of the arithmetic mean roughness Ra of the surface 13S of the magnetic layer 13 is 1.0 nm or more, it is possible to suppress a decrease in runnability due to an increase in friction.

The arithmetic mean roughness Ra of the surface 13S is determined as follows. First, the surface of the magnetic layer 13 is observed using an AFM (Atomic Force Microscope) to obtain an AFM image of 40 μm×40 μm. The AFM is Nano Scope IIIa D3100 manufactured by Digital Instruments, the cantilever is made of silicon single crystal, and the tapping frequency is tuned to 200 Hz to 400 Hz for measurement. As the cantilever, for example, "SPM probe NCH normal type PointProbe L (cantilever length) = 125 um" manufactured by Nano World can be used. Next, the AFM image is divided into 512×512 (=262,144) measurement points, and the height Z(i) (i: measurement point number, i=1 to 262,144) is measured at each measurement point. Simply average (arithmetic mean) the height Z(i) of each measured point and calculate the average height (average surface) Zave(=(Z(1)+Z(2)+...+Z(262,144))/ 262,144). Next, the deviation Z"(i) (=|Z(i)-Zave|) from the average center line at each measurement point is calculated, and the arithmetic mean roughness Ra [nm] (=(Z"(1)+Z "(2)+...+Z" (262,144))/262,144) is calculated. At this time, image processing is performed using flatten order 2 and planefit order 3 XY filtering processing as data.

Further, in the magnetic layer 13, it is desirable that the PSD (Power Spectrum Density) up to a spatial wavelength of 5 μm is, for example, 2.5 μm or less. By suppressing the PSD below a certain value, the spacing between the recording/reproducing head and the tape-shaped magnetic recording medium 10 during recording and reproduction can be reduced, making the magnetic recording medium 10 suitable for high recording density. be able to. Measurement of PSD is performed as follows. The analysis mode Power Spectral Density (attached analysis software) is performed on the data after the filter processing described in paragraph 0022 above. For the data to be analyzed, only the longitudinal direction (X) of the sample is selected and processed from the measurement data, and after saving in an ASC file format, the data is processed in an Excel file. Regarding the amplitude data of each frequency, the sum of the amplitude data of 5 μm or less is calculated and set as PDS.

The lower limit of the entire BET specific surface area of the magnetic recording medium 10 in a state where the lubricant is removed is 2.5 m ² /g or more, preferably 3.0 m ² /g or more, more preferably 3.5 m ² /g or more. , even more preferably 4.0 m ² /g or more. If the lower limit of the BET specific surface area is 2.5 m ² /g or more, even after repeated recording or reproduction (that is, even after repeatedly running the magnetic head in contact with the surface of the magnetic recording medium 10) , it is possible to suppress a decrease in the amount of lubricant supplied between the surface of the magnetic layer 13 and the magnetic head. Therefore, an increase in the coefficient of dynamic friction can be suppressed.

The upper limit of the entire BET specific surface area of the magnetic recording medium 10 in a state where the lubricant is removed is preferably 7 m ² /g or less, more preferably 6 m ² /g or less, and even more preferably 5.5 m ² /g or less. It is. When the upper limit of the BET specific surface area is 7 m ² /g or less, the lubricant can be sufficiently supplied without being depleted even after many runs. Therefore, an increase in the coefficient of dynamic friction can be suppressed.

The magnetic recording medium 10 in a state with the lubricant removed herein refers to the magnetic recording medium 10 in a state in which the magnetic recording medium 10 is immersed in hexane at room temperature for 24 hours, then taken out from the hexane and air-dried. means.

The BET specific surface area is determined as follows.

First, a magnetic recording medium 10 whose size is about 10% larger than an area of 0.1265 m ² is immersed in hexane (an amount sufficient to immerse the magnetic recording medium 10, for example, 150 ml of hexane) for 24 hours, and then air-dried. A measurement sample is prepared by cutting it into a size with an area of 0.1265 m ² (for example, cut off 50 cm from both ends of the dried magnetic recording medium 10 to prepare a magnetic recording medium 10 having a width of 10 m). Next, the BET specific surface area is determined using a specific surface area/pore distribution measuring device. The measuring device and measurement conditions are shown below.
Measurement environment: Room temperature Measuring device: 3FLEX manufactured by Micromeritics
Measured adsorbate: _N2 gas measurement pressure range (P/P0): 0 to 0.995
Regarding the measurement pressure range, the pressure was changed as shown in Table 1 below. The pressure values in Table 1 below are relative pressures P/P0. In the table below, for example, in step 1, the pressure is changed from a starting pressure of 0.000 to an ultimate pressure of 0.010, changing by 0.001 per 10 seconds. Once the pressure reaches the ultimate pressure, the next step of pressure change is performed. The same applies to steps 2 to 10. However, in each step, if the pressure has not reached equilibrium, the device waits for the pressure to reach equilibrium before moving on to the next step.

The upper limit of the average thickness of the magnetic layer 13 is preferably 90 nm or less, particularly preferably 80 nm or less, more preferably 70 nm or less, and even more preferably 60 nm or less. When the upper limit of the average thickness of the magnetic layer 13 is 90 nm or less, magnetization can be recorded uniformly in the thickness direction of the magnetic layer 13 when a ring-type head is used as the recording head, improving electromagnetic conversion characteristics. be able to. Further, if the upper limit of the average thickness of the magnetic layer 13 is 90 nm or less, the half width of the isolated waveform in the reproduced waveform of the data signal is narrowed (for example, to 200 nm or less), and the peak of the reproduced waveform of the data signal is sharpened. be able to. This improves the accuracy of reading data signals, so it is possible to increase the number of recording tracks and improve the data recording density.

The lower limit of the average thickness of the magnetic layer 13 is preferably 35 nm or more. When the upper limit of the average thickness of the magnetic layer 13 is 35 nm or more, when an MR type head is used as a reproducing head, output can be ensured and electromagnetic conversion characteristics can be improved.

The average thickness of the magnetic layer 13 is determined as follows. First, a carbon film is formed on the surface 13S of the magnetic layer 13 and the surface 14S of the back layer 14 of the magnetic recording medium 10 by a vapor deposition method, and then a tungsten thin film is formed on the carbon film covering the surface 13S of the magnetic layer 13 by a vapor deposition method. Form further. These carbon films and tungsten films protect the sample during the thinning process described later.

Next, the magnetic recording medium 10 is processed into a thin section by the FIB (Focused Ion Beam) method or the like. When using the FIB method, a carbon film and a tungsten thin film are formed as a protective film as a pretreatment for observing a TEM image of a cross section, which will be described later. The carbon film is formed on the magnetic layer side surface and the back layer side surface of the magnetic recording medium 10 by a vapor deposition method, and the tungsten thin film is further formed on the magnetic layer side surface by a vapor deposition method or a sputtering method. The thinning is performed along the length direction (longitudinal direction) of the magnetic recording medium 10. That is, by thinning, a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium 10 is formed. The cross section of the obtained thinned sample is observed using a transmission electron microscope (TEM) under the following conditions to obtain a TEM image. Note that the magnification and acceleration voltage may be adjusted as appropriate depending on the type of device.
Equipment: TEM (H9000NAR manufactured by Hitachi)
Acceleration voltage: 300kV
Magnification: 100,000x

Next, the thickness of the magnetic layer 13 is measured at at least ten positions in the longitudinal direction of the magnetic recording medium 10 using the obtained TEM image. The average value obtained by simply averaging (arithmetic average) the obtained measured values is defined as the average thickness of the magnetic layer 13. Note that the position where the measurement is performed is randomly selected from the test piece.

(Magnetic powder)
The magnetic powder includes, for example, powder of nanoparticles containing ε iron oxide (hereinafter referred to as "ε iron oxide particles"). Epsilon iron oxide particles can obtain high coercive force even in fine particles. The epsilon iron oxide contained in the epsilon iron oxide particles is preferably crystallized preferentially in the thickness direction (perpendicular direction) of the magnetic recording medium 10.

FIG. 2 is a cross-sectional view schematically showing an example of the cross-sectional structure of the ε iron oxide particles 20 included in the magnetic layer 13. As shown in FIG. 2, the epsilon iron oxide particles 20 have a spherical or approximately spherical shape, or a cubic or approximately cubic shape. Since the ε iron oxide particles 20 have the above-described shape, when the ε iron oxide particles 20 are used as the magnetic particles, the magnetic The contact area between particles in the thickness direction of the recording medium 10 can be reduced, and aggregation of particles can be suppressed. Therefore, it is possible to improve the dispersibility of the magnetic powder and obtain a better SNR (Signal-to-Noise Ratio).

The ε iron oxide particles 20 have, for example, a core-shell structure. Specifically, the ε iron oxide particles 20 include a core portion 21 and a two-layer shell portion 22 provided around the core portion 21, as shown in FIG. The two-layer shell portion 22 includes a first shell portion 22a provided on the core portion 21 and a second shell portion 22b provided on the first shell portion 22a.

The core portion 21 of the ε iron oxide particles 20 contains ε iron oxide. The ε-iron oxide contained in the core portion 21 preferably has ε-Fe ₂ O ₃ crystal as its main phase, and more preferably consists of single-phase ε-Fe ₂ O ₃ .

The first shell portion 22a covers at least a portion of the periphery of the core portion 21. Specifically, the first shell portion 22a may partially cover the periphery of the core portion 21, or may cover the entire periphery of the core portion 21. From the viewpoint of ensuring sufficient exchange coupling between the core part 21 and the first shell part 22a and improving magnetic properties, it is preferable that the entire surface of the core part 21 be covered.

The first shell portion 22a is a so-called soft magnetic layer, and includes a soft magnetic material such as α-Fe, Ni-Fe alloy, or Fe-Si-Al alloy. α-Fe may be obtained by reducing ε iron oxide contained in the core portion 21.

The second shell portion 22b is an oxide film serving as an oxidation prevention layer. The second shell portion 22b contains alpha iron oxide, aluminum oxide, or silicon oxide. The α iron oxide contains, for example, at least one kind of iron oxide among Fe ₃ O ₄ , Fe ₂ O ₃ and FeO. When the first shell portion 22a includes α-Fe (soft magnetic material), α-iron oxide may be obtained by oxidizing α-Fe contained in the first shell portion 22a.

Since the ε iron oxide particles 20 have the first shell portion 22a as described above, the ε iron oxide particles (core shell The coercive force Hc of the particle) 20 as a whole can be adjusted to a coercive force Hc suitable for recording. Further, since the ε iron oxide particles 20 have the second shell portion 22b as described above, the ε iron oxide particles 20 are exposed to air during the manufacturing process of the magnetic recording medium 10 and before that process, and the particle surface It is possible to suppress the deterioration of the properties of the ε iron oxide particles 20 due to the occurrence of rust or the like. Therefore, by covering the first shell portion 22a with the second shell portion 22b, deterioration of the characteristics of the magnetic recording medium 10 can be suppressed.

The average particle size (average maximum particle size) of the magnetic powder is preferably 25 nm or less, more preferably 8 nm or more and 22 nm or less, and even more preferably 12 nm or more and 22 nm or less. In the magnetic recording medium 10, an area whose size is 1/2 of the recording wavelength becomes an actual magnetized area. Therefore, by setting the average particle size of the magnetic powder to less than half the shortest recording wavelength, a good S/N ratio can be obtained. Therefore, when the average particle size of the magnetic powder is 22 nm or less, good electromagnetic properties can be achieved in a high recording density magnetic recording medium 10 (for example, a magnetic recording medium 10 configured to be able to record signals at the shortest recording wavelength of 50 nm or less). Conversion characteristics (eg SNR) can be obtained. On the other hand, when the average particle size of the magnetic powder is 8 nm or more, the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (for example, SNR) can be obtained.

The average aspect ratio of the magnetic powder is preferably 1.0 or more and 3.0 or less, more preferably 1.0 or more and 2.8 or less, and even more preferably 1.0 or more and 2.0 or less. When the average aspect ratio of the magnetic powder is within the range of 1 or more and 3.0 or less, agglomeration of the magnetic powder can be suppressed, and when the magnetic powder is vertically aligned in the process of forming the magnetic layer 13, the magnetic powder It is possible to suppress the resistance added to the Therefore, the vertical orientation of the magnetic powder can be improved.

The average particle size and average aspect ratio of the above magnetic powder are determined as follows. First, the magnetic recording medium 10 to be measured is processed into a thin section by the FIB (Focused Ion Beam) method or the like. The thinning is performed along the length direction (longitudinal direction) of the magnetic tape. That is, by this thinning, a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic recording medium 10 is formed. The obtained thin sample was examined using a transmission electron microscope (Hitachi High Technologies H-9500) at an accelerating voltage of 200 kV and a total magnification of 500,000 times, so that the entire magnetic layer 13 was included in the thickness direction of the magnetic layer 13. Observe the cross section and take a TEM photograph. Next, 50 particles are randomly selected from the taken TEM photograph, and the long axis length DL and short axis length DS of each particle are measured. Here, the long axis length DL means the maximum distance between two parallel lines drawn from any angle so as to be in contact with the contour of each particle (so-called maximum Feret diameter). On the other hand, the short axis length DS means the maximum length of the particle in the direction perpendicular to the long axis length DL of the particle.

Subsequently, the average long axis length DLave is determined by simply averaging (arithmetic mean) the long axis lengths DL of the 50 measured particles. The average major axis length DLave thus determined is defined as the average particle size of the magnetic powder. Further, the average short axis length DSave is obtained by simply averaging (arithmetic mean) the short axis lengths DS of the 50 measured particles. Then, the average aspect ratio (DLave/DSave) of the particles is determined from the average major axis length DLave and the average minor axis length DSave.

The average particle volume of the magnetic powder is preferably 2300 nm ³ or less, more preferably 2200 nm ³ or less, more preferably 2100 nm ^{3 or less, more preferably 1950 nm 3 or} less, more preferably 1600 nm ³ or less, even more preferably 1300 nm ^{3 or} less. be. When the average particle volume of the magnetic powder is 2300 nm ³ or less, the half width of the isolated waveform in the reproduced data signal waveform can be narrowed (200 nm or less), and the peak of the reproduced data signal waveform can be sharpened. This improves the accuracy of reading data signals, so it is possible to increase the number of recording tracks and improve the data recording density (details will be described later). Note that the lower average particle volume of the magnetic powder is better as it is smaller, so the lower limit of the volume is not particularly limited, but the lower limit is, for example, 1000 nm ³ or more.

When the ε iron oxide particles 20 have a spherical or nearly spherical shape, the average particle volume of the magnetic powder is determined as follows. First, the average major axis length DLave is determined in the same manner as the method for calculating the average particle size of the magnetic powder described above. Next, the average volume V of the magnetic powder is determined using the following formula.
V=(π/6)×(DLave) ³

(binder)
As the binder, a resin having a structure obtained by imparting a crosslinking reaction to a polyurethane resin, a vinyl chloride resin, or the like is preferable. However, the binder is not limited to these, and other resins may be appropriately blended depending on the physical properties required for the magnetic recording medium 10. The resin to be blended is not particularly limited as long as it is a resin commonly used in the coating type magnetic recording medium 10.

For example, polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-chlorinated Vinyl-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic ester-vinylidene chloride copolymer, methacrylic ester-chloride Vinyl copolymers, methacrylic acid ester-ethylene copolymers, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymers, acrylonitrile-butadiene copolymers, polyamide resins, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose dichloromethane) acetate, cellulose triacetate, cellulose propionate, nitrocellulose), styrene-butadiene copolymer, polyester resin, amino resin, synthetic rubber, and the like.

Further, examples of thermosetting resins or reactive resins include phenol resins, epoxy resins, urea resins, melamine resins, alkyd resins, silicone resins, polyamine resins, urea formaldehyde resins, and the like.

In addition, polar functional groups such as -SO ₃ M, -OSO ₃ M, -COOM, and P=O(OM) ₂ are introduced into each of the above-mentioned binders for the purpose of improving the dispersibility of the magnetic powder. You can leave it there. Here, M in the above chemical formula is a hydrogen atom or an alkali metal such as lithium, potassium, or sodium.

Further, examples of the polar functional group include side chain types having terminal groups of -NR1R2 and -NR1R2R3 ⁺ X ^- , and main chain types having >NR1R2 ⁺ X ^- . Here, R1, R2, and R3 in the above formula are hydrogen atoms or hydrocarbon groups, and ^X- is a halogen element ion such as fluorine, chlorine, bromine, or iodine, or an inorganic or organic ion. Further, examples of the polar functional group include -OH, -SH, -CN, and epoxy group.

(lubricant)
The lubricant contained in the magnetic layer 13 contains, for example, fatty acids and fatty acid esters. The fatty acid contained in the lubricant preferably contains at least one of a compound represented by the following general formula <1> and a compound represented by the general formula <2>, for example. Further, the fatty acid ester contained in the lubricant preferably contains at least one of a compound represented by the following general formula <3> and a compound represented by the general formula <4>. The lubricant contains two types of compounds, the compound represented by the general formula <1> and the compound represented by the general formula <3>, so that the compound represented by the general formula <2> and the compound represented by the general formula <3> are obtained. By including two types of the compound represented by the general formula <1> and the compound represented by the general formula <4>, the compound represented by the general formula <2> and the compound represented by the general formula <4> By including two types of compounds represented by general formula <1>, by including three types of compounds represented by general formula <2>, and by including three types of compounds represented by general formula <3>, the general By including three types of compounds represented by formula <1>, the compound represented by general formula <2>, and the compound represented by general formula <4>, the compound represented by general formula <1>, the compound represented by general formula <3>> and the compound represented by general formula <4>, the compound represented by general formula <2>, the compound represented by general formula <3>, and the compound represented by general formula <4> are included. or a compound represented by general formula <1>, a compound represented by general formula <2>, a compound represented by general formula <3>, and a compound represented by general formula <4>. By including the four types of compounds, it is possible to suppress an increase in the coefficient of dynamic friction due to repeated recording or reproduction in the magnetic recording medium 10. As a result, the running performance of the magnetic recording medium 10 can be further improved.
CH ₃ (CH ₂ ) _k COOH ... <1>
(However, in the general formula <1>, k is an integer selected from the range of 14 to 22, more preferably 14 to 18.)
CH ₃ (CH ₂ ) _n CH=CH (CH ₂ ) _m COOH ...<2>
(However, in the general formula <2>, the sum of n and m is an integer selected from the range of 12 to 20, more preferably 14 to 18.)
CH ₃ (CH ₂ ) _p COO (CH ₂ ) _q CH ₃ ...<3>
(However, in general formula <3>, p is an integer selected from the range of 14 to 22, more preferably 14 to 18, and q is in the range of 2 to 5, more preferably 2 to 4 (It is an integer selected from the following range.)
CH ₃ (CH ₂ ) _p COO-(CH ₂ ) _q CH(CH ₃ ) ₂ …<4>
(However, in the general formula <4>, p is an integer selected from the range of 14 to 22, and q is an integer selected from the range of 1 to 3.)

(Additive)
The magnetic layer 13 contains aluminum oxide (α, β or γ alumina), chromium oxide, silicon oxide, diamond, garnet, emery, boron nitride, titanium carbide, silicon carbide, titanium carbide, titanium oxide ( It may further contain rutile type or anatase type titanium oxide).

(base layer 12)
Underlayer 12 is a nonmagnetic layer containing nonmagnetic powder and a binder. The base layer 12 may further contain at least one additive selected from a lubricant, conductive particles, a hardening agent, a rust preventive, and the like, if necessary. Further, the base layer 12 may have a multilayer structure in which a plurality of layers are stacked. The average thickness of the base layer 12 is preferably 0.4 μm or more and 1.4 μm or less, more preferably 0.6 μm or more and 1.2 μm or less.

Note that the average thickness of the base layer 12 is determined, for example, as follows. First, a 1/2 inch wide magnetic recording medium 10 is prepared and cut into a length of 250 mm to produce a sample. Subsequently, with respect to the sample magnetic recording medium 10, the underlayer 12 and the magnetic layer 13 are peeled off from the base 11. Next, using a laser hologage (LGH-110C) manufactured by Mitutoyo as a measuring device, the thickness of the laminate of the base layer 12 and magnetic layer 13 peeled off from the base 11 is measured at five or more positions. do. Thereafter, the measured values are simply averaged (arithmetic averaged) to calculate the average thickness of the laminate of the underlayer 12 and the magnetic layer 13. Note that the measurement position is randomly selected from the sample. Finally, the average thickness of the underlayer 12 is determined by subtracting the average thickness of the magnetic layer 13 measured using the TEM as described above from the average thickness of the laminate.

It is preferable that the base layer 12 has a large number of holes. By storing lubricant in these many holes, the magnetic layer remains stable even after repeated recording or reproduction (that is, even after repeatedly moving the magnetic head in contact with the surface of the magnetic recording medium 10). It is possible to further suppress a decrease in the amount of lubricant supplied between the surface 13S of the magnetic head 13 and the magnetic head. Therefore, it is possible to further suppress an increase in the coefficient of dynamic friction.

From the viewpoint of suppressing a decrease in the coefficient of dynamic friction after repeated recording or reproduction, it is preferable that the holes in the underlayer 12 and the holes in the magnetic layer 13 are connected. Here, the expression that the holes in the underlayer 12 and the holes in the magnetic layer 13 are connected means that some of the many holes in the underlayer 12 and some of the many holes in the magnetic layer 13 are connected to each other. This includes the state where some of the items are connected.

From the viewpoint of improving the supply of lubricant to the surface 13S of the magnetic layer 13, it is preferable that the large number of holes include holes extending perpendicularly to the surface 13S of the magnetic layer 13. . In addition, from the viewpoint of improving the supply of lubricant to the surface 13S of the magnetic layer 13, the holes in the underlayer 12 extending perpendicularly to the surface 13S of the magnetic layer 13 and the surface of the magnetic layer 13 It is preferable that the hole of the magnetic layer 13 extending perpendicularly to the magnetic layer 13S is connected to the hole.

(Non-magnetic powder of base layer 12)
The non-magnetic powder includes, for example, at least one of inorganic particle powder and organic particle powder. Further, the non-magnetic powder may include carbon powder such as carbon black. Note that one type of non-magnetic powder may be used alone, or two or more types of non-magnetic powder may be used in combination. Inorganic particles include, for example, metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, metal sulfides, and the like. Examples of the shape of the non-magnetic powder include various shapes such as acicular, spherical, cubic, and plate-like, but are not limited thereto.

(Binder for base layer 12)
The binder in the underlayer 12 is the same as that in the magnetic layer 13 described above.

(Back layer 14)
The back layer 14 contains, for example, a binder and nonmagnetic powder. The back layer 14 may further contain at least one additive selected from a lubricant, a curing agent, an antistatic agent, and the like, if necessary. The binder and nonmagnetic powder in the back layer 14 are the same as the binder and nonmagnetic powder in the base layer 12 described above.

The average particle size of the nonmagnetic powder in the back layer 14 is preferably 10 nm or more and 150 nm or less, more preferably 15 nm or more and 110 nm or less. The average particle size of the non-magnetic powder in the back layer 14 is determined in the same manner as the average particle size of the magnetic powder in the magnetic layer 13 described above. The non-magnetic powder may include one having two or more particle size distributions.

The upper limit of the average thickness of the back layer 14 is preferably 0.6 μm or less, particularly preferably 0.5 μm or less. If the upper limit of the average thickness of the back layer 14 is 0.6 μm or less, even if the average thickness of the magnetic recording medium 10 is 5.6 μm or less, the thickness of the underlayer 12 and the base 11 can be kept thick. , it is possible to maintain running stability of the magnetic recording medium 10 within the recording/reproducing apparatus. The lower limit of the average thickness of the back layer 14 is not particularly limited, but is, for example, 0.2 μm or more, particularly preferably 0.3 μm or more.

The average thickness of the back layer 14 is determined as follows. First, a 1/2 inch wide magnetic recording medium 10 is prepared and cut into a length of 250 mm to produce a sample. Next, using a laser hologage (LGH-110C) manufactured by Mitutoyo as a measuring device, the thickness of the sample magnetic recording medium 10 is measured at five or more points, and the measured values are simply averaged ( (arithmetic mean) to calculate the average thickness t _T [μm] of the magnetic recording medium 10. Note that the measurement position is randomly selected from the sample. Subsequently, the back layer 14 is removed from the sample magnetic recording medium 10 using a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. After that, using the laser hologage mentioned above again, measure the thickness of the sample from which the back layer 14 has been removed from the magnetic recording medium 10 at five or more points, and simply average (arithmetic mean) these measured values to calculate the thickness of the back layer. The average thickness t _B [μm] of the magnetic recording medium 10 from which 14 is removed is calculated. Note that the measurement position is randomly selected from the sample. Finally, the average thickness t _b [μm] of the back layer 14 is determined from the following formula.
t _b [μm] = t _T [μm] - t _B [μm]

The back layer 14 has a surface provided with a large number of protrusions. The large number of protrusions are for forming a large number of holes on the surface of the magnetic layer 13 when the magnetic recording medium 10 is rolled up. The large number of holes are made up of, for example, a large number of nonmagnetic particles protruding from the surface of the back layer 14.

Here, a case has been described in which a large number of holes are formed on the surface of the magnetic layer 13 by transferring a large number of protrusions provided on the surface of the back layer 14 to the surface of the magnetic layer 13. The method of forming the part is not limited to this. For example, a large number of holes may be formed on the surface of the magnetic layer 13 by adjusting the type of solvent contained in the magnetic layer forming paint and the drying conditions of the magnetic layer forming paint.

[Average thickness of magnetic recording medium]
The upper limit of the average thickness (average total thickness) of the magnetic recording medium 10 is preferably 5.6 μm or less, more preferably 5.0 μm or less, particularly preferably 4.6 μm or less, and even more preferably 4.4 μm or less. . When the average thickness of the magnetic recording medium 10 is 5.6 μm or less, the recording capacity that can be recorded in one data cartridge can be increased compared to a general magnetic recording medium. The lower limit of the average thickness of the magnetic recording medium 10 is not particularly limited, but is, for example, 3.5 μm or more.

The average thickness tT of the magnetic recording medium 10 is determined as follows. First, a 1/2 inch wide magnetic recording medium 10 is prepared and cut into a length of 250 mm to produce a sample. Next, the thickness of the sample is measured at five or more positions using a Mitutoyo Laser Hologage (LGH-110C) as a measuring device, and the measured values are simply averaged (arithmetic mean). Calculate the value tT [μm]. Note that the measurement position is randomly selected from the sample.

(Coercive force Hc1 in the vertical direction)
The upper limit of the coercive force Hc1 in the vertical direction is 3000 Oe or less, more preferably 2900 Oe or less, even more preferably 2850 Oe or less. It is preferable that the coercive force Hc1 is large because it is less susceptible to thermal disturbances and demagnetizing fields. However, if the coercive force Hc1 exceeds 3000 Oe, it becomes difficult for the recording head to perform saturation recording, and as a result, there are areas that cannot be recorded, noise increases, and as a result, there is a risk that electromagnetic conversion characteristics (for example, C/N) may deteriorate. There is.

The lower limit of the coercive force Hc1 in the vertical direction is preferably 2200 Oe or more, more preferably 2400 Oe or more, even more preferably 2600 Oe or more. When the coercive force Hc1 is 2200 Oe or more, it is possible to suppress deterioration of electromagnetic conversion characteristics (for example, C/N) in a high-temperature environment due to the influence of thermal disturbance and the influence of a demagnetizing field.

The above coercive force Hc1 is determined as follows. A measurement sample is prepared by stacking three magnetic recording media 10 and adhering them with double-sided tape, and then punching them out with a punch of φ6.39 mm. At this time, marking is performed using any non-magnetic ink so that the longitudinal direction (running direction) of the magnetic recording medium can be recognized. Then, using a vibrating sample magnetometer (VSM), an MH loop of a measurement sample (the entire magnetic recording medium 10) corresponding to the longitudinal direction of the magnetic recording medium 10 (travel direction of the magnetic recording medium 10) is performed. Measure. Next, the coating film (base layer 12, magnetic layer 13, back layer 14, etc.) is wiped off using acetone, ethanol, or the like, leaving only the base 11. Then, three of the obtained substrates 11 are stacked and adhered with double-sided tape, and then punched with a punch of φ6.39 mm to obtain a background correction sample (hereinafter simply referred to as a correction sample). Thereafter, the MH loop of the correction sample (substrate 11) corresponding to the vertical direction of the substrate 11 (thickness direction of the magnetic recording medium 10) is measured using the VSM.

In the measurement of the MH loop of the measurement sample (the entire magnetic recording medium 10) and the MH loop of the correction sample (substrate 11), for example, a sensitive vibrating sample magnetometer manufactured by Toei Kogyo ``VSM-P7- 15 type" is used. The measurement conditions are: measurement mode: full loop, maximum magnetic field: 15 kOe, magnetic field step: 40 bits, time constant of locking amp: 0.3 sec, waiting time: 1 sec, and average number of MHs: 20.

After obtaining the two MH loops, background correction is performed by subtracting the MH loop of the correction sample (substrate 11) from the MH loop of the measurement sample (the entire magnetic recording medium 10). , the MH loop after background correction is obtained. The measurement and analysis program attached to the "VSMP7-15" is used to calculate this background correction.

The coercive force Hc1 is determined from the obtained MH loop after background correction. Note that this calculation uses the measurement and analysis program attached to the "VSM-P7-15 type". Note that all of the above MH loop measurements are performed at 25°C. Further, it is assumed that "demagnetizing field correction" is not performed when measuring the MH loop in the direction perpendicular to the magnetic recording medium 10.

(Coercive force Hc2 in longitudinal direction)
The upper limit of the coercive force Hc2 in the longitudinal direction of the magnetic recording medium 10 is preferably 2000 Oe or less, more preferably 1900 Oe or less, even more preferably 1800 Oe or less. When the coercive force Hc2 in the longitudinal direction is 2000 Oe or less, the magnetization responds sensitively to the perpendicular magnetic field from the recording head, so that a good recording pattern can be formed.

The lower limit of the coercive force Hc2 measured in the longitudinal direction of the magnetic recording medium 10 is preferably 1000 Oe or more. When the lower limit of the coercive force Hc in the longitudinal direction is 1000 Oe or more, demagnetization due to magnetic flux leakage from the recording head can be suppressed.

The above coercive force Hc2 is a coercive force in the vertical direction, except that the entire measurement sample and the MH loop of the sample for background correction are measured in the direction corresponding to the longitudinal direction (running direction) of the magnetic recording medium 10. It is obtained in the same manner as Hc1.

(Hc2/Hc1)
The ratio Hc2/Hc1 of the coercive force Hc1 in the vertical direction and the coercive force Hc2 in the longitudinal direction is Hc2/Hc1≦0.8, preferably Hc2/Hc1≦0.75, more preferably Hc2/Hc1≦0.7, Even more preferably, the relationship Hc2/Hc1≦0.65 is satisfied, particularly preferably Hc2/Hc1≦0.6. When the coercive forces Hc1 and Hc2 satisfy the relationship Hc2/Hc1≦0.8, the degree of vertical orientation of the magnetic powder can be increased. Therefore, it is possible to reduce the magnetization transition width and obtain a high-output signal during signal reproduction, so that electromagnetic conversion characteristics (for example, C/N) can be improved. Note that, as described above, when Hc2 is small, the magnetization reacts with high sensitivity to the perpendicular magnetic field from the recording head, so that a good recording pattern can be formed.

When the ratio Hc2/Hc1 is Hc2/Hc1≦0.8, it is particularly effective that the average thickness of the magnetic layer 13 is 90 nm or less. If the average thickness of the magnetic layer 13 exceeds 90 nm, when a ring-type head is used as a recording head, the lower region of the magnetic layer 13 (the region on the underlayer 12 side) will be magnetized in the longitudinal direction, and the magnetic layer 13 will be magnetized in the longitudinal direction. There is a risk that it will not be possible to magnetize uniformly in the thickness direction. Therefore, even if the ratio Hc2/Hc1 is set to Hc2/Hc1≦0.8 (that is, even if the degree of vertical orientation of the magnetic powder is increased), it may not be possible to improve the electromagnetic conversion characteristics (for example, C/N). .

The lower limit value of Hc2/Hc1 is not particularly limited, but is, for example, 0.5≦Hc2/Hc1.

Note that Hc2/Hc1 represents the degree of vertical orientation of the magnetic powder, and the smaller Hc2/Hc1, the higher the degree of vertical orientation of the magnetic powder. The reason why Hc2/Hc1 is used as an index indicating the degree of vertical orientation of magnetic powder in this embodiment will be explained below.

Conventionally, the index (parameter) that generally indicates the degree of vertical orientation of magnetic powder is the squareness ratio SQ (= (Mr/Ms) x 100, where Mr (emu): residual magnetization, Ms (emu): saturation. magnetization) has been used. However, according to the findings of the present inventors, the squareness ratio SQ is not suitable as an index indicating the degree of vertical orientation of magnetic powder for the following reasons.
(1) The squareness ratio SQ varies depending on the value of the coercive force Hc of the magnetic powder. For example, as shown in FIG. 5, when the coercive force Hc of the magnetic powder increases, the apparent squareness ratio SQ also becomes a large value.
(2) The squareness ratio SQ is affected by distortion of the MH loop due to overdispersion.

Therefore, in this embodiment, Hc2/Hc1 is used as an index that more appropriately indicates the degree of orientation of magnetic powder. Since the coercive forces Hc1 and Hc2 simply change depending on the orientation direction of the magnetic powder, Hc2/Hc1 is more suitable as an index indicating the degree of orientation of the magnetic powder.

(Square ratio)
The squareness ratio S1 in the vertical direction (thickness direction) of the magnetic recording medium 10 is, for example, 65% or more, preferably 70% or more, more preferably 75% or more, even more preferably 80% or more, particularly preferably 85%. That's all. When the squareness ratio S1 is 65% or more, the vertical orientation of the magnetic powder becomes sufficiently high, so that a more excellent SNR can be obtained.

The squareness ratio S1 is determined as follows. A measurement sample is prepared by stacking three magnetic recording media 10 and adhering them with double-sided tape, and then punching them out with a punch of φ6.39 mm. At this time, marking is performed using any non-magnetic ink so that the longitudinal direction (running direction) of the magnetic recording medium can be recognized. Then, using a vibrating sample magnetometer (VSM), an MH loop of a measurement sample (the entire magnetic recording medium 10) corresponding to the longitudinal direction of the magnetic recording medium 10 (travel direction of the magnetic recording medium 10) is performed. Measure. Next, the coating film (base layer 12, magnetic layer 13, back layer 14, etc.) is wiped off using acetone, ethanol, or the like, leaving only the base 11. Then, three of the obtained substrates 11 are stacked and adhered with double-sided tape, and then punched with a punch of φ6.39 mm to obtain a background correction sample (hereinafter simply referred to as a correction sample). Thereafter, the MH loop of the correction sample (substrate 11) corresponding to the longitudinal direction of the substrate 11 (the running direction of the magnetic recording medium 10) is measured using the VSM.

In the measurement of the MH loop of the measurement sample (the entire magnetic recording medium 10) and the MH loop of the correction sample (substrate 11), for example, a sensitive vibrating sample magnetometer manufactured by Toei Kogyo ``VSM-P7- 15 type" is used. The measurement conditions are: measurement mode: full loop, maximum magnetic field: 15 kOe, magnetic field step: 40 bits, time constant of locking amp: 0.3 sec, waiting time: 1 sec, and average number of MHs: 20.

After obtaining the two MH loops, background correction is performed by subtracting the MH loop of the correction sample (substrate 11) from the MH loop of the measurement sample (the entire magnetic recording medium 10). , the MH loop after background correction is obtained. The measurement and analysis program attached to the "VSMP7-15" is used to calculate this background correction.

The obtained saturation magnetization Ms (emu) and residual magnetization Mr (emu) of the MH loop after background correction are substituted into the following formula to calculate the squareness ratio S1 (%).
Squareness ratio S1 (%) = (Mr/Ms) x 100
Note that all of the above MH loop measurements are performed at 25°C. Further, it is assumed that "demagnetizing field correction" is not performed when measuring the MH loop in the direction perpendicular to the magnetic recording medium 10.

The squareness ratio S2 in the longitudinal direction (running direction) of the magnetic recording medium 10 is preferably 35% or less, more preferably 30% or less, even more preferably 25% or less, particularly preferably 20% or less, and most preferably 15%. It is as follows. When the squareness ratio S2 is 35% or less, the vertical orientation of the magnetic powder becomes sufficiently high, so that a more excellent SNR can be obtained.

The squareness ratio S2 is determined in the same manner as the squareness ratio S1, except that the MH loop is measured in the longitudinal direction (running direction) of the magnetic recording medium 10 and the substrate 11.

(SFD)
In the SFD (Switching Field Distribution) curve of the magnetic recording medium 10, the peak ratio X/Y between the main peak height X and the sub-peak height Y near zero magnetic field is preferably 3.0 or more, more preferably It is 5.0 or more, even more preferably 7.0 or more, particularly preferably 10.0 or more, and most preferably 20.0 or more (see FIG. 3). When the peak ratio It can suppress the amount contained in powder. Therefore, it is possible to suppress the deterioration of the magnetization signals recorded in the adjacent tracks due to the leakage magnetic field from the recording head, so that a better SNR can be obtained. The upper limit of the peak ratio X/Y is not particularly limited, but is, for example, 100 or less.

The above peak ratio X/Y is determined as follows. First, an MH loop after background correction is obtained in the same manner as the method for measuring the coercive force Hc described above. Next, an SFD curve is calculated from the obtained MH loop. A program attached to the measuring device may be used to calculate the SFD curve, or another program may be used. Let "Y" be the absolute value of the point where the calculated SFD curve crosses the Y axis (dM/dH), and let "X" be the height of the main peak seen near the coercive force Hc in the MH loop. Calculate the peak ratio X/Y. Note that the measurement of the MH loop is carried out at 25° C. in the same manner as the method for measuring the coercive force Hc described above. Further, when measuring the MH loop in the thickness direction (perpendicular direction) of the magnetic recording medium 10, "demagnetizing field correction" is not performed. Furthermore, depending on the sensitivity of the VSM used, the MH loop may be measured by stacking a plurality of samples to be measured.

(activation volume Vact)
The activation volume Vact is preferably 8000 nm ³ or less, more preferably 6000 nm ³ or less, even more preferably 5000 nm ³ or less, particularly preferably 4000 nm ³ or less, most preferably 3000 nm ^{3 or} less. When the activation volume Vact is 8000 nm ³ or less, the magnetic powder is well dispersed, so the bit reversal region can be made steep, and the leakage magnetic field from the recording head can reduce the magnetization recorded in adjacent tracks. Signal deterioration can be suppressed. Therefore, better SNR is obtained.

The above activation volume Vact is determined by the following formula derived by Street & Woolley.
Vact (nm ³ )=kB×T×Χirr/(μ0×Ms×S)
(However, kB: Boltzmann constant (1.38×10 ^-23 J/K), T: temperature (K), Χirr: irreversible magnetic susceptibility, μ0: magnetic permeability of vacuum, S: magnetorheological coefficient, Ms: saturation Magnetization (emu/cm ³ ))

The irreversible magnetic susceptibility Χirr, the saturation magnetization Ms, and the magnetorheological coefficient S substituted into the above equation are obtained as follows using VSM. The measurement sample used for VSM is prepared by punching out three magnetic recording media 10 stacked with double-sided tape with a punch of φ6.39 mm. At this time, marking is performed using any non-magnetic ink so that the longitudinal direction (running direction) of the magnetic recording medium 10 can be recognized. Note that the measurement direction by VSM is the thickness direction (vertical direction) of the magnetic recording medium 10. Further, it is assumed that the measurement by VSM is performed at 25° C. on a measurement sample cut out from the elongated magnetic recording medium 10. Further, when measuring the MH loop in the thickness direction (perpendicular direction) of the magnetic recording medium 10, "demagnetizing field correction" is not performed. Furthermore, in the measurement of the M-H loop of the measurement sample (the entire magnetic recording medium 10) and the M-H loop of the correction sample (substrate 11), a high-sensitivity vibrating sample magnetometer "VSM" manufactured by Toei Kogyo Co., Ltd. -P7-15 type” is used. The measurement conditions are: measurement mode: full loop, maximum magnetic field: 15 kOe, magnetic field step: 40 bits, time constant of locking amp: 0.3 sec, waiting time: 1 sec, and average number of MHs: 20.

(irreversible magnetic susceptibility Χirr)
The irreversible magnetic susceptibility Χirr is defined as the slope of the residual magnetization curve (DCD curve) near the residual magnetic force Hr. First, a magnetic field of -1193 kA/m (15 kOe) is applied to the entire magnetic recording medium 10, and the magnetic field is returned to zero to create a residual magnetization state. Thereafter, a magnetic field of about 15.9 kA/m (200 Oe) is applied in the opposite direction to return the magnet to zero and measure the amount of residual magnetization. Thereafter, a magnetic field that is 15.9 kA/m larger than the previously applied magnetic field is applied and the measurement is repeated to return to zero, and the amount of residual magnetization is plotted against the applied magnetic field to measure the DCD curve. From the obtained DCD curve, the point at which the amount of magnetization becomes zero is defined as the residual magnetic force Hr, and the DCD curve is further differentiated to determine the slope of the DCD curve in each magnetic field. In the slope of this DCD curve, the slope near the residual magnetic force Hr is Χirr.

(Saturation magnetization Ms)
First, an MH loop after background correction is obtained in the same manner as the method for measuring the coercive force Hc described above. Next, Ms (emu/cm ³ ) is calculated from the value of the obtained saturation magnetization Ms (emu) of the MH loop and the volume (cm ³ ) of the magnetic layer 13 in the measurement sample. Note that the volume of the magnetic layer 13 is determined by multiplying the area of the measurement sample by the average thickness of the magnetic layer 13. The method for calculating the average thickness of the magnetic layer 13 necessary for calculating the volume of the magnetic layer 13 is as described above.

(Magneto-rheological coefficient S)
First, a magnetic field of -1193 kA/m (15 kOe) is applied to the entire magnetic recording medium 10 (measurement sample) to return the magnetic field to zero and create a residual magnetization state. Thereafter, a magnetic field equivalent to the value of the residual magnetic force Hr obtained from the DCD curve is applied in the opposite direction. The amount of magnetization is continuously measured at regular time intervals for 1000 seconds while a magnetic field is applied. The magnetorheological coefficient S is calculated by comparing the thus obtained relationship between the time t and the amount of magnetization M(t) with the following formula.
M(t)=M0+S×ln(t)
(However, M(t): amount of magnetization at time t, M0: amount of initial magnetization, S: magnetorheological coefficient, ln(t): natural logarithm of time)

(data band and servo band)
FIG. 4 is a schematic diagram of the magnetic recording medium 10 viewed from above. As shown in FIG. 4, the magnetic layer 13 has a plurality of data bands DB (data bands DB0 to DB3 are shown in FIG. 4) extending in the longitudinal direction (X-axis direction) of the magnetic recording medium 10, and magnetic recording It has a plurality of servo bands SB (servo bands SB0 to SB4 are shown in FIG. 4) extending in the longitudinal direction (X-axis direction) of the medium 10. Data signals are written into each of the plurality of data bands DB, and servo signals for tracking control of the magnetic head are written into each of the plurality of servo bands SB. Moreover, each data band DB is arranged so as to be sandwiched between a plurality of servo bands SB adjacent to each other in the width direction (Y-axis direction).

The upper limit of the ratio R _S (=(S _SB /S)×100) of the total area S _SB of the servo band S to the area S of the surface 13S of the magnetic layer 13 is preferably 4 from the viewpoint of ensuring a high recording capacity. .0% or less, more preferably 3.0% or less, even more preferably 2.0% or less. On the other hand, the lower limit of the ratio R _S of the total area S SB of the servo band SB to the area S of the surface of the magnetic layer ₁₃ is preferably 0.8% or more from the viewpoint of ensuring 5 or more servo tracks.

The ratio R _S of the total area S SB of the servo band SB to the area S of the surface 13S of the magnetic layer 13 is, for example, the ratio R _S of the total area S SB of the servo band SB to the area S of the surface 13S of the magnetic layer 13. The measurement can be carried out by developing the magnetic recording medium 10 using an optical microscope and then observing the developed magnetic recording medium 10 with an optical microscope. The servo band width W _SB and the number of servo bands SB are measured from an image observed with an optical microscope. Next, the ratio R _S is determined from the following formula.
Ratio R _S [%] = (((servo band width W _SB )×(number of servo bands))/(width of magnetic recording medium 10))×100

The number of servo bands SB is preferably 5 or more, more preferably 5+4n (where n is a positive integer) or more. When the number of servo bands SB is 5 or more, it is possible to suppress the influence on servo signals due to dimensional changes in the width direction of the magnetic recording medium 10, and to ensure stable recording and reproducing characteristics with less off-track.

The upper limit value of the servo bandwidth W _SB is preferably 95 μm or less, more preferably 60 μm or less, and even more preferably 30 μm or less, from the viewpoint of ensuring high recording capacity. The lower limit of the servo band width W _SB is preferably 10 μm or more from the viewpoint of manufacturing the recording head. The width of the servo band width _WSB is determined as follows. First, the magnetic recording medium 10 is developed using a ferricolloid developer (Sigma Car Q, manufactured by Sigma High Chemical Co., Ltd.). Next, by observing the developed magnetic recording medium 10 with an optical microscope, the width of the servo band width _WSB can be measured.

As shown in FIG. 4, the data band DB can form a plurality of recording tracks 5 that extend along the X-axis direction and are aligned adjacently in the Y-axis direction. A data signal is recorded along this recording track 5 and within the recording track 5 . Note that in the present technology, the length of one bit in the longitudinal direction (distance between magnetization reversals) in the data signal recorded in the data band DB is typically 48 nm or less. The servo band SB includes a predetermined servo signal recording pattern 6 in which servo signals are recorded by a servo signal recording device (not shown).

FIG. 5 is an enlarged view showing the recording track 5 in the data band DB. As shown in FIG. 5, each recording track 5 has a predetermined recording track width Wd in the Y-axis direction. The recording track width Wd is typically 3.0 μm or less. Note that such recording track width Wd is measured by, for example, developing the magnetic recording medium 10 using a developer such as a ferricolloid developer, and then observing the developed magnetic recording medium 10 with an optical microscope. be able to.

The number of recording tracks 5 included in one data band DB is, for example, about 1000 to 2000.

FIG. 6 is an enlarged view showing the servo signal recording pattern 6 in the servo band SB. As shown in FIG. 6, the servo signal recording pattern 6 includes a plurality of stripes 7 that are inclined at a predetermined azimuth angle α with respect to the width direction (Y-axis direction). The plurality of stripes 7 are classified into a first stripe group 8 that slopes clockwise with respect to the width direction (Y-axis direction) and a second stripe group 9 that slopes counterclockwise with respect to the width direction. be done. The shape of the stripes 7 can be determined by, for example, developing the magnetic recording medium 10 using a developer such as a ferricolloid developer, and then observing the developed magnetic recording medium 10 with an optical microscope. can be measured.

In FIG. 6, a servo trace line T, which is a line traced by a servo read head on the servo signal recording pattern 6, is shown by a broken line. The servo trace lines T are set along the longitudinal direction (X-axis direction), and are set at predetermined intervals Ps in the width direction.

The number of servo trace lines T per one servo band SB is, for example, about 30 to 60.

The distance Ps between two adjacent servo trace lines T is the same as the recording track width Wd, and is, for example, 2.0 μm or less. Here, the interval Ps between two adjacent servo trace lines T is a value that determines the recording track width Wd. That is, when the interval Ps between the servo trace lines T is narrowed, the recording track width Wd becomes smaller, and the number of recording tracks 5 included in one data band DB increases. As a result, the data recording capacity increases (and vice versa when the interval Ps becomes wider). Therefore, in order to increase the recording capacity, it is necessary to reduce the recording track width Wd, but this also reduces the interval Ps between the servo trace lines T, making it difficult to accurately trace adjacent servo trace lines. become. Therefore, in this embodiment, as will be described later, by narrowing the reproduced signal width, that is, the half width of the isolated waveform in the reproduced waveform of the data signal, it is possible to cope with the narrowing of the recording track width Wd.

(Friction coefficient ratio (μ _B /μ _A ))
The coefficient of dynamic friction μA between the surface 13S of the magnetic layer 13 of the magnetic recording medium 10 and the magnetic head when a tension of 0.4 N is applied in the longitudinal direction of the magnetic recording medium 10, and 1 in the longitudinal direction of the magnetic recording medium 10. The friction coefficient ratio (μB/μA) between the surface 13S of the magnetic layer 13 of the magnetic recording medium 10 and the magnetic head under a tension of .2N and the dynamic friction coefficient μB is preferably 1.0 or more and 2 .1 or less, more preferably 1.2 or more and 1.8 or less. When the friction coefficient ratio (μB/μA) is 1.0 or more and 2.1 or less, changes in the dynamic friction coefficient due to tension fluctuations during running can be reduced, so that running of the magnetic recording medium 10 can be stabilized.

The dynamic friction coefficient μA and the dynamic friction coefficient μB for calculating the friction coefficient ratio (μB/μA) are obtained as follows. First, as shown in FIG. 7, a 1/2 inch wide magnetic recording medium 10 is placed between two 1 inch diameter cylindrical guide rolls 91 and 92 which are spaced apart from each other and arranged in parallel. Place it so that the surfaces 13S of the two are in contact with each other. The two guide rolls 91 and 92 are fixed in position with respect to each other.

Next, the surface 13S of the magnetic layer 13 of the magnetic recording medium 10 is brought into contact with the head block (for recording and reproduction) 93 mounted on the LTO5 drive, and the included angle θ1 [°] = 5.6°. One end of the magnetic recording medium 10 is gripped by a gripping jig 94 and connected to a movable strain gauge 95. A weight 96 is suspended from the other end of the magnetic recording medium 10, and a tension T0 of 0.4N is applied. Give. Note that the head block 74 is fixed at a position where the embrace angle θ1 [°] is 5.6°. Thereby, the positional relationship between the guide rolls 91, 92 and the head block 93 is also fixed.

Next, by the movable strain gauge 95, the magnetic recording medium 10 is slid 60 mm toward the movable strain gauge 95 with respect to the head block 93 at a speed of 10 mm/s. The output value (voltage) of the movable strain gauge 95 during this sliding is converted into T[N] based on a linear relationship between the output value and the load (described later) that has been obtained in advance. Obtain T[N] 13 times from the start of the 60 mm slide to the stop of the slide, and simply average the 11 T[N] excluding the first and last two times. Thus, T _ave [N] is obtained.
Then, calculate the dynamic friction coefficient _μA using the following formula.

The above linear relationship is obtained as follows. That is, the output value (voltage) of the movable strain gauge 95 is obtained for each case where a load of 0.4 N is applied to the movable strain gauge 95 and when a load of 1.5 N is applied to the movable strain gauge 95. A linear relationship between the output value and the load is obtained from the two obtained output values and the two loads. Using this linear relationship, as described above, the output value (voltage) from the movable strain gauge 95 during sliding is converted into T[N].

The dynamic friction coefficient μB is measured in the same manner as the dynamic friction coefficient μA, except that the tension T0 applied to the other end of the magnetic recording medium 10 is set to 1.2N.

A friction coefficient ratio (μB/μA) is calculated from the dynamic friction coefficient μA and the dynamic friction coefficient μB measured as described above.

If the kinetic friction coefficient between the surface 13S of the magnetic layer 13 and the magnetic head is μC when the tension applied to the magnetic recording medium 10 is 0.6N, then the kinetic friction coefficient μC(5) at the fifth time from the start of the run and the start of the run. The friction coefficient ratio (μC(1000)/μC(5)) with respect to the 1000th dynamic friction coefficient μC(1000) is preferably 1.0 or more and 1.8 or less, more preferably 1.0 or more and 1.6 or less. It is. When the friction coefficient ratio (μC(1000)/μC(5)) is 1.0 or more and 1.8 or less, changes in the dynamic friction coefficient due to multiple runs can be reduced, thereby stabilizing the running of the magnetic recording medium 10. be able to. Here, it is assumed that a drive compatible with the magnetic recording medium 10 is used as the magnetic head.

(Friction coefficient ratio (μ _C(1000) / μ _C(5) ))
The dynamic friction coefficient μC(5) and the dynamic friction coefficient μC(1000) for calculating the friction coefficient ratio (μC(1000)/μC(5)) are obtained as follows.

Preferably, the magnetic recording medium 10 has a dynamic friction coefficient μ _{C( 5)} and the dynamic friction coefficient μ _C(1000) at the 1000th reciprocation when the magnetic head is reciprocated 1000 times (μ _{C (1000)} / μ _{C (5)} ) is 1.0 to 2. .0, more preferably 1.0 to 1.8, even more preferably 1.0 to 1.6. By having the friction coefficient ratio (μ _{C (1000)} / μ _{C (5)} ) within the above numerical range, changes in the dynamic friction coefficient due to multiple runs can be reduced, so that the running of the magnetic recording medium 10 is stabilized. can be done.

さらに、動摩擦係数μ_C(1000)は、１０００回目の往路の測定をすること以外は動摩擦係数μ_C(5)と同様にして求める。
以上のとおりにして測定された動摩擦係数μ_C(5)及び動摩擦係数μ_C(1000)から、摩擦係数比μ_C(1000)／μ_C(5)が算出される。 The dynamic friction coefficient μ C( _{5) and the dynamic friction coefficient μ C (1000)} for calculating the friction coefficient ratio (μ _C(1000) /μ _C(5) ) are obtained as follows.
The magnetic recording medium 10 was moved to the movable strain gauge 71 in the same manner as the method for measuring the coefficient of dynamic friction _μA , except that the tension T ₀ [N] applied to the other end of the magnetic recording medium 10 was set to 0.6N. Connect with. Then, the magnetic recording medium 10 is slid 60 mm toward the movable strain gauge with respect to the head block 74 at 10 mm/s (outward path) and 60 mm away from the movable strain gauge (return path). This reciprocating motion is repeated 1000 times. Among these 1000 reciprocating movements, the output value (voltage) of the strain gauge was obtained 13 times between the start of the 60 mm sliding movement on the 5th outward movement and the stop of the sliding movement, and the dynamic friction coefficient μ _A It is converted to T[N] based on the linear relationship between the output value and the load determined in (described later). T _ave [N] is obtained by simply averaging the 11 times excluding the first and last two times.
The dynamic friction coefficient μ _C(5) is determined by the following formula.

Further, the dynamic friction coefficient μ _{C (1000)} is obtained in the same manner as the dynamic friction coefficient μ _{C (5)} except that the 1000th outbound measurement is performed.
The friction coefficient ratio μ _{C ( 1000} ) / μ C (5 _{) is calculated from the dynamic friction coefficient μ C (5) and the dynamic friction coefficient μ C (1000 )} measured as described above.

[1-2 Method for manufacturing magnetic recording medium 10]
Next, a method for manufacturing the magnetic recording medium 10 having the above-described configuration will be described. First, a paint for forming a base layer is prepared by kneading and dispersing non-magnetic powder, a binder, a lubricant, etc. in a solvent. Next, a paint for forming a magnetic layer is prepared by kneading and dispersing magnetic powder, a binder, a lubricant, etc. in a solvent. Next, a paint for forming a back layer is prepared by kneading and dispersing a binder, nonmagnetic powder, etc. in a solvent. For preparing the paint for forming the magnetic layer, the paint for forming the base layer, and the paint for forming the back layer, the following solvents, dispersing devices, and kneading devices can be used, for example.

Examples of solvents used in the above paint preparation include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, alcohol solvents such as methanol, ethanol, and propanol, methyl acetate, ethyl acetate, butyl acetate, and propyl acetate. , ester solvents such as ethyl lactate and ethylene glycol acetate, ether solvents such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, and dioxane, aromatic hydrocarbon solvents such as benzene, toluene, and xylene, methylene chloride, ethylene chloride, Examples include halogenated hydrocarbon solvents such as carbon tetrachloride, chloroform, and chlorobenzene. These may be used alone or in an appropriate mixture.

As the kneading device used for preparing the above-mentioned paint, for example, a continuous twin-screw kneader, a continuous twin-screw kneader capable of diluting in multiple stages, a kneader, a pressure kneader, a roll kneader, etc. can be used. , but is not particularly limited to these devices. In addition, examples of dispersion equipment used in the above-mentioned paint preparation include roll mills, ball mills, horizontal sand mills, vertical sand mills, spike mills, pin mills, tower mills, pearl mills (for example, "DCP Mill" manufactured by Eirich, etc.), homogenizers, super Although a dispersion device such as a sonic dispersion machine can be used, the present invention is not particularly limited to these devices.

Next, the base layer 12 is formed by applying a base layer forming paint to one main surface 11A of the base 11 and drying it. Subsequently, the magnetic layer 13 is formed on the base layer 12 by applying a magnetic layer forming paint onto the base layer 12 and drying it. Note that during drying, it is preferable to orient the magnetic powder in the thickness direction of the substrate 11 using a magnetic field, for example, using a solenoid coil. Further, during drying, the magnetic powder may be magnetically oriented in the running direction (longitudinal direction) of the base 11 using, for example, a solenoid coil, and then the magnetic powder may be oriented in the thickness direction of the base 11. By performing such a magnetic field orientation treatment, the degree of vertical orientation (that is, the squareness ratio S1) of the magnetic powder can be improved. After forming the magnetic layer 13, a back layer forming paint is applied to the other main surface 11B of the base 11 and dried to form the back layer 14. As a result, a magnetic recording medium 10 is obtained.

The squareness ratios S1, S2 and the ratio Hc2/Hc1 are determined by, for example, the intensity of the magnetic field applied to the coating film of the magnetic layer forming paint, the concentration of solid content in the magnetic layer forming paint, and the coating film of the magnetic layer forming paint. The desired value is set by adjusting the drying conditions (drying temperature and drying time). The strength of the magnetic field applied to the coating film is preferably at least twice the coercive force of the magnetic powder. In order to further increase the squareness ratio S1 (that is, to further lower the squareness ratio S2), it is preferable to improve the state of dispersion of the magnetic powder in the coating material for forming the magnetic layer. In order to further increase the squareness ratio S1, it is also effective to magnetize the magnetic powder before the magnetic layer forming paint enters the orientation device for orienting the magnetic powder in a magnetic field. Note that the above methods for adjusting the squareness ratios S1 and S2 may be used alone or in combination of two or more.

Thereafter, the obtained magnetic recording medium 10 is calendered to smooth the surface 13S of the magnetic layer 13. Next, the calendered magnetic recording medium 10 is wound up into a roll, and in this state, the magnetic recording medium 10 is subjected to heat treatment to make the many protrusions on the surface 14S of the back layer 14 magnetic. It is transferred onto the surface 13S of the layer 13. As a result, a large number of holes are formed on the surface 13S of the magnetic layer 13.

The temperature of the heat treatment is preferably 50°C or higher and 80°C or lower. When the temperature of the heat treatment is 50° C. or higher, good transferability can be obtained. On the other hand, if the temperature of the heat treatment is 80° C. or lower, the number of pores becomes too large, and there is a risk that there will be too much lubricant on the surface 13S of the magnetic layer 13. Here, the temperature of the heat treatment is the temperature of the atmosphere in which the magnetic recording medium 10 is held.

The heat treatment time is preferably 15 hours or more and 40 hours or less. When the heat treatment time is 15 hours or more, good transferability can be obtained. On the other hand, when the heat treatment time is 40 hours or less, it is possible to suppress a decrease in productivity.

Further, the pressure applied to the magnetic recording medium 10 during the heat treatment is preferably in a range of 150 kg/cm or more and 400 kg/cm or less.

Finally, the magnetic recording medium 10 is cut into a predetermined width (for example, 1/2 inch width). Through the above steps, the desired magnetic recording medium 10 can be obtained.

[1-3 Configuration of recording/reproducing device 30]
Next, with reference to FIG. 8, a configuration of a recording/reproducing apparatus 30 that records information on the above-described magnetic recording medium 10 and reproduces information from the above-described magnetic recording medium 10 will be described.

The recording/reproducing device 30 has a configuration that can adjust the tension applied to the magnetic recording medium 10 in the longitudinal direction. Further, the recording/reproducing device 30 has a configuration in which a magnetic recording medium cartridge 10A can be loaded therein. Here, for ease of explanation, a case will be described in which the recording/reproducing apparatus 30 has a configuration in which one magnetic recording medium cartridge 10A can be loaded. However, in the present disclosure, the recording/reproducing device 30 may have a configuration in which a plurality of magnetic recording medium cartridges 10A can be loaded. As mentioned above, the magnetic recording medium 10 is tape-shaped, and may be a long magnetic recording tape, for example. The magnetic recording medium 10 may be housed in a housing while being wound around a reel inside the magnetic recording medium cartridge 10A, for example. The magnetic recording medium 10 is designed to be run in the longitudinal direction during recording and reproduction. Further, the magnetic recording medium 10 may be configured to be able to record a signal at a shortest recording wavelength of preferably 100 nm or less, more preferably 75 nm or less, even more preferably 60 nm or less, particularly preferably 50 nm or less, such as the shortest recording wavelength. It can be used in a recording/reproducing device 30 whose wavelength is within the above range. The recording track width may be, for example, 2 μm or less.

The recording/reproducing device 30 is connected to information processing devices such as a server 41 and a personal computer (hereinafter referred to as "PC") 42 via a network 43, for example, and magnetically records data supplied from these information processing devices. It is configured to be recordable on the medium cartridge 10A.

As shown in FIG. 8, the recording and reproducing device 30 includes a spindle 31, a reel 32, a drive device 33, a drive device 34, a plurality of guide rollers 35, a head unit 36, and a communication interface (hereinafter referred to as I). /F) 37 and a control device 38.

The spindle 31 is configured such that the magnetic recording medium cartridge 10A can be attached thereto. The magnetic recording medium cartridge 10A complies with the LTO (Linear Tape Open) standard, and rotatably accommodates a single reel 10C on which the magnetic recording medium 10 is wound in a cartridge case 10B. A V-shaped servo pattern is recorded in advance on the magnetic recording medium 10 as a servo signal. The reel 32 is configured to be able to fix the leading end of the magnetic recording medium 10 pulled out from the magnetic recording medium cartridge 10A.

The drive device 33 is a device that rotates the spindle 31. The drive device 34 is a device that rotates the reel 32. When recording or reproducing data on the magnetic recording medium 10, the drive device 33 and the drive device 34 rotate the spindle 31 and the reel 32, respectively, thereby causing the magnetic recording medium 10 to travel. The guide roller 35 is a roller for guiding the running of the magnetic recording medium 10.

The head unit 36 includes a plurality of recording heads for recording data signals on the magnetic recording medium 10 and a plurality of reproducing heads for reproducing the data signals recorded on the magnetic recording medium 10. For example, a ring-type head can be used as the recording head, and a magnetoresistive magnetic head, for example, can be used as the reproducing head, but the types of the recording head and the reproducing head are not limited to these.

The I/F 37 is for communicating with information processing devices such as the server 41 and the PC 42, and is connected to the network 43.

The control device 38 controls the entire recording/reproducing device 30 . For example, the control device 38 records data signals supplied from the information processing devices, such as the server 41 and the PC 42, on the magnetic recording medium 10 using the head unit 36. Further, in response to requests from information processing devices such as the server 41 and the PC 42, the control device 38 reproduces data signals recorded on the magnetic recording medium 10 using the head unit 36, and supplies the reproduced data signals to the information processing devices.

[1-4 Effect]
As described above, the magnetic recording medium 10 of the present embodiment is a tape-shaped member in which the base 11, the underlayer 12, and the magnetic layer 13 are laminated in this order, and has the following configurations (1) to (9). It is designed to meet the requirements.
(1) The base 11 contains polyester as a main component.
(2) The magnetic layer 13 is provided on the base 11, contains a plurality of magnetic powders, and is capable of recording data signals.
(3) The average thickness of the magnetic recording medium is 5.6 μm or less.
(4) The average thickness of the substrate is 4.2 μm or less.
(5) The average thickness of the magnetic layer 13 is 90 nm or less.
(6) The average aspect ratio of the magnetic powder in the magnetic layer 13 is 1.0 or more and 3.0 or less. (7) The coercive force Hc1 in the vertical direction is 3000 Oe or less.
(8) The ratio Hc2/Hc1 of the coercive force Hc2 in the longitudinal direction to the coercive force Hc1 in the vertical direction is 0.8 or less.
(9) The entire BET specific surface area of the magnetic recording medium in a state where the lubricant is removed is 2.5 m ² /g or more.

By having such a configuration, the magnetic recording medium 10 of the present embodiment can maintain good electromagnetic conversion characteristics (for example, C/N) while making the magnetization transition width steep. In addition, when repeatedly recording and/or reproducing, the lubricant can be stably present on the surface of the magnetic recording medium, and an increase in friction due to sliding can be suppressed. Furthermore, since the average thickness of the magnetic recording medium 10 is 5.6 μm or less and the average thickness of the base 11 is 4.2 μm or less, the storage capacity that can be recorded in one magnetic recording medium cartridge 10A (see FIG. 8) can be increased more than before. Therefore, a configuration advantageous for high-density recording can be realized.

Further, in the magnetic recording medium 10 of the present embodiment, if the entire BET specific surface area of the magnetic recording medium in a state where the lubricant is removed is 3.0 m ² /g or more, the BET specific surface area is 3.0 m ² /g. The friction coefficient ratio (μB/μA) can be reduced compared to the case where the magnetic recording medium 10 is less than g, and the change in the dynamic friction coefficient due to tension fluctuations during running becomes smaller, so that the running of the magnetic recording medium 10 can be made more stable.

Further, in the magnetic recording medium 10 of the present embodiment, if the entire BET specific surface area of the magnetic recording medium in a state where the lubricant is removed is 3.5 m ² /g or more, the BET specific surface area is 3.5 m ² /g. The friction coefficient ratio (μB/μA) can be further reduced compared to the case where the magnetic recording medium 10 is less than g, and the change in the dynamic friction coefficient due to tension fluctuations during running is smaller, so the running of the magnetic recording medium 10 can be made more stable. . In particular, if the entire BET specific surface area of the magnetic recording medium in a state where the lubricant is removed is set to 4.0 m ² /g or more, the running of the magnetic recording medium 10 can be made even more stable.

Further, in the magnetic recording medium 10 of the present embodiment, when the friction coefficient ratio (μC(1000)/μC(5)) is 1.0 or more and 1.8 or less, the change in the dynamic friction coefficient due to multiple runs is reduced. Therefore, the running of the magnetic recording medium 10 can be stabilized.

Further, in the magnetic recording medium 10 of the present embodiment, when the average particle diameter of the magnetic powder is 8 nm or more and 22 nm or less, good electromagnetic conversion characteristics (for example, SNR) can be obtained in the magnetic recording medium 10.

In addition, in the magnetic recording medium 10 of the present embodiment, when the average particle volume of the plurality of magnetic powders is 2300 nm ³ or less, the half width of the isolated waveform in the reproduced waveform of the data signal is narrowed, and the reproduced waveform of the data signal is can sharpen the peak of This improves the accuracy of reading data signals, so it is possible to increase the number of recording tracks and improve the data recording density.

Further, in the magnetic recording medium 10 of this embodiment, excellent electromagnetic conversion characteristics can be obtained if the arithmetic mean roughness Ra of the surface of the magnetic layer 13 is 2.5 nm or less. Further, if the PSD up to a spatial wavelength of 5 μm is 2.5 μm or less, the spacing between the recording/reproducing head and the tape-shaped magnetic recording medium 10 during recording and reproduction can be reduced, and the magnetic recording medium 10 is suitable for high recording density.

In addition, in the magnetic recording medium 10 of this embodiment, when the coercive force in the longitudinal direction is 2000 Oe or less, the magnetization responds sensitively to the perpendicular magnetic field from the recording head, so that a good recording pattern can be formed. I can do it.

In addition, in the magnetic recording medium 10 of the present embodiment, the ratio Hc2/Hc1 of the coercive force Hc2 in the longitudinal direction to the coercive force Hc1 in the vertical direction satisfies the relationship Hc2/Hc1≦0.7, so that the magnetic powder can increase the degree of vertical orientation. Therefore, it is possible to reduce the magnetization transition width and obtain a high-output signal during signal reproduction, so that electromagnetic conversion characteristics (for example, C/N) can be improved.

In addition, in the magnetic recording medium 10 of the present embodiment, when the coercive force Hc1 in the perpendicular direction is 2200 Oe or more, electromagnetic conversion characteristics (for example, C/N) in a high temperature environment due to the influence of thermal disturbance and the influence of a demagnetizing field are It is possible to suppress the decrease in

<2. Modified example>
(Modification 1)
In the embodiment described above, the epsilon iron oxide particles 20 (FIG. 2) having the shell portion 22 having a two-layer structure have been described as an example, but the magnetic recording medium of the present technology can be configured as shown in FIG. 9, for example. , the ε iron oxide particles 20A having a single-layer shell portion 23 may be included. The shell portion 23 in the ε iron oxide particle 20A has, for example, the same configuration as the first shell portion 22a. However, from the viewpoint of suppressing characteristic deterioration, the ε iron oxide particles 20 having the two-layer shell portion 22 described in the above embodiment are preferable to the ε iron oxide particles 20A of Modification 1.

(Modification 2)
In the magnetic recording medium 10 of the above-described embodiment, the epsilon iron oxide particles 20 having a core-shell structure have been described as an example, but the epsilon iron oxide particles may contain an additive instead of the core-shell structure, or It has a core-shell structure and may contain additives. In this case, part of the Fe in the ε iron oxide particles is replaced by the additive. When the epsilon iron oxide particles contain an additive, the coercive force Hc of the epsilon iron oxide particles as a whole can be adjusted to a coercive force Hc suitable for recording, so that ease of recording can be improved. The additive is a metal element other than iron, preferably a trivalent metal element, more preferably at least one of Al (aluminum), Ga (gallium) and In (indium), even more preferably Al and Ga. At least one of them.

Specifically, ε-iron oxide containing additives is a ε-Fe ₂ -xMxO ₃ crystal (where M is a metal element other than iron, preferably a trivalent metal element, more preferably Al, Ga, and In). At least one of them, and even more preferably at least one of Al and Ga. x is, for example, 0<x<1.

(Modification 3)
The magnetic powder of the present disclosure may include powder of nanoparticles containing hexagonal ferrite (hereinafter referred to as "hexagonal ferrite particles") instead of powder of ε iron oxide particles. The hexagonal ferrite particles have, for example, a hexagonal plate shape or a substantially hexagonal plate shape. The hexagonal ferrite preferably contains at least one of Ba (barium), Sr (strontium), Pb (lead), and Ca (calcium), more preferably at least one of Ba and Sr. The hexagonal ferrite may specifically be, for example, barium ferrite or strontium ferrite. Barium ferrite may further contain at least one of Sr, Pb, and Ca in addition to Ba. Strontium ferrite may further contain at least one of Ba, Pb, and Ca in addition to Sr.

More specifically, hexagonal ferrite has an average composition represented by the general formula MFe ₁₂ O ₁₉ . However, M is, for example, at least one metal selected from Ba, Sr, Pb, and Ca, preferably at least one metal selected from Ba and Sr. M may be a combination of Ba and one or more metals selected from the group consisting of Sr, Pb, and Ca. Furthermore, M may be a combination of Sr and one or more metals selected from the group consisting of Ba, Pb, and Ca. In the above general formula, a part of Fe may be substituted with another metal element.

When the magnetic powder includes a powder of hexagonal ferrite particles, the average particle size of the magnetic powder is preferably 50 nm or less, more preferably 40 nm or less, and even more preferably 30 nm or less. The average particle size of the magnetic powder is preferably 25 nm or less, 22 nm or less, 21 nm or less, or 20 nm or less. Further, the average particle size of the magnetic powder is, for example, 10 nm or more, preferably 12 nm or more, and more preferably 15 nm or more. Therefore, the average particle size of the magnetic powder containing hexagonal ferrite particle powder can be, for example, 10 nm or more and 50 nm or less, 10 nm or more and 40 nm or less, 12 nm or more and 30 nm or less, 12 nm or more and 25 nm or less, or 15 nm or more and 22 nm or less. When the average particle size of the magnetic powder is equal to or less than the above upper limit (e.g., 50 nm or less, particularly 30 nm or less), good electromagnetic conversion characteristics (e.g., SNR) can be obtained in the high recording density magnetic recording medium 10. I can do it. When the average particle size of the magnetic powder is at least the above lower limit (for example, at least 10 nm, preferably at least 12 nm), the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (for example, SNR) are obtained. be able to.

When the magnetic powder includes powder of hexagonal ferrite particles, the average aspect ratio of the magnetic powder is preferably 1 or more and 3.5 or less, more preferably 1 or more and 3.1 or less, or 2 or more and 3.1 or less, and even more. Preferably, the number may be 2 or more and 3 or less. By having the average aspect ratio of the magnetic powder within the above numerical range, agglomeration of the magnetic powder can be suppressed, and furthermore, when the magnetic powder is vertically aligned in the process of forming the magnetic layer 13, the resistance applied to the magnetic powder can be suppressed. can be suppressed. This can lead to improved vertical alignment of the magnetic powder.

Note that the average particle size and average aspect ratio of the magnetic powder containing the hexagonal ferrite particle powder are determined as follows. First, the magnetic recording medium 10 to be measured is processed into a thin section by the FIB (Focused Ion Beam) method or the like. The thinning is performed along the length direction (longitudinal direction) of the magnetic tape. The obtained thin sample was examined using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies) at an accelerating voltage of 200 kV and a total magnification of 500,000 times so that the entire recording layer was included in the thickness direction of the recording layer. Perform cross-sectional observation. Next, from the taken TEM photograph, 50 particles with their side faces facing the observation surface are selected, and the maximum plate thickness DA of each particle is measured. The maximum plate thicknesses DA obtained in this manner are simply averaged (arithmetic mean) to obtain the average maximum plate thickness DAave. Subsequently, the plate diameter DB of each magnetic powder is measured. Here, the plate diameter DB means the maximum distance (so-called maximum Feret diameter) among the distances between two parallel lines drawn from any angle so as to be in contact with the contour of the magnetic powder. Subsequently, the average plate diameter DBave is obtained by simply averaging (arithmetic mean) the measured plate diameters DB. Then, the average aspect ratio (DBave/DAave) of the particles is determined from the average maximum plate thickness DAave and the average plate diameter DBave.

When the magnetic powder includes powder of hexagonal ferrite particles, the average particle volume of the magnetic powder is preferably 5900 nm ³ or less, more preferably 500 nm ³ or more and 3400 nm ³ or less, and even more preferably 1000 nm ³ or more and 2500 nm ^{3 or} less. When the average particle volume of the magnetic powder is 5900 nm ³ or less, the same effect as when the average particle size of the magnetic powder is 30 nm or less can be obtained. On the other hand, when the average particle volume of the magnetic powder is 500 nm ³ or more, the same effect as when the average particle size of the magnetic powder is 12 nm or more can be obtained.

Note that the average particle volume of the magnetic powder is determined as follows. First, the average maximum plate thickness DAave and the average maximum plate diameter DBave are determined by the method for calculating the average particle size of magnetic powder described above. Next, the average volume V of the ε iron oxide particles is determined using the following formula.

According to a particularly preferred embodiment of the present technology, the magnetic powder may be barium ferrite magnetic powder or strontium ferrite magnetic powder, more preferably barium ferrite magnetic powder. Barium ferrite magnetic powder includes magnetic particles of iron oxide having barium ferrite as a main phase (hereinafter referred to as "barium ferrite particles"). Barium ferrite magnetic powder has high reliability in data recording, with its coercive force not decreasing even in high-temperature and humid environments. From this point of view, barium ferrite magnetic powder is preferable as magnetic powder.

The average particle size of the barium ferrite magnetic powder is 50 nm or less, more preferably 10 nm or more and 40 nm or less, and even more preferably 12 nm or more and 25 nm or less.

When the magnetic layer 13 contains barium ferrite magnetic powder as the magnetic powder, the average thickness tm [nm] of the magnetic layer 13 is preferably 35 nm≦tm≦100 nm, particularly preferably 80 nm or less. Further, the coercive force Hc measured in the thickness direction (vertical direction) of the magnetic recording medium 10 is preferably 160 kA/m or more and 280 kA/m or less, more preferably 165 kA/m or more and 275 kA/m or less, and even more preferably 170 kA/m or less. m or more and 270 kA/m or less.

(Modification 4)
The magnetic powder may include powder of nanoparticles containing Co-containing spinel ferrite (hereinafter referred to as "cobalt ferrite particles") instead of powder of ε iron oxide particles. It is preferable that the cobalt ferrite particles have uniaxial anisotropy. The cobalt ferrite particles have, for example, a cubic or nearly cubic shape. The Co-containing spinel ferrite may further contain at least one of Ni, Mn, Al, Cu, and Zn in addition to Co.

Co-containing spinel ferrite has, for example, an average composition represented by the following formula.
C _x M _y Fe ₂ O _Z
(However, in formula (1), M is, for example, at least one metal selected from Ni, Mn, Al, Cu, and Zn. x is within the range of 0.4≦x≦1.0. y is a value within the range of 0≦y≦0.3.However, x and y satisfy the relationship (x+y)≦1.0.z is within the range of 3≦z≦4 is the value. Part of Fe may be substituted with another metal element.)

When the magnetic powder includes powder of cobalt ferrite particles, the average particle size of the magnetic powder is preferably 25 nm or less, more preferably 10 nm or more and 23 nm or less. When the average particle size of the magnetic powder is 25 nm or less, good electromagnetic conversion characteristics (for example, SNR) can be obtained in the high recording density magnetic recording medium 10. On the other hand, when the average particle size of the magnetic powder is 10 nm or more, the dispersibility of the magnetic powder is further improved, and better electromagnetic conversion characteristics (for example, SNR) can be obtained. When the magnetic powder includes powder of cobalt ferrite particles, the average aspect ratio of the magnetic powder is the same as in the above embodiment. Further, the average particle size and average aspect ratio of the magnetic powder are also determined in the same manner as the calculation method of the above-mentioned embodiment.

The average particle volume of the magnetic powder is preferably 15,000 nm ³ or less, more preferably 1,000 nm ³ or more and 12,000 nm ³ or less. When the average particle volume of the magnetic powder is 15,000 nm ³ or less, the same effect as when the average particle size of the magnetic powder is 25 nm or less can be obtained. On the other hand, when the average particle volume of the magnetic powder is 1000 nm ³ or more, the same effect as when the average particle size of the magnetic powder is 10 nm or more can be obtained. The average particle volume of the magnetic powder is determined by the method of calculating the average particle volume of the magnetic powder in the above-mentioned embodiment (the method of calculating the average particle volume when the ε iron oxide particles have a cubic or almost cubic shape). ).

The coercive force Hc of the cobalt ferrite magnetic powder is preferably 2,500 Oe or more, more preferably 2,600 Oe or more and 3,500 Oe or less.

(Modification 5)
The magnetic recording medium 10 may further include a barrier layer provided on at least one surface of the base 11. This barrier layer is a layer for suppressing dimensional changes in the base 11 depending on the environment. For example, one of the causes of the dimensional change is the hygroscopicity of the base 11, and by providing a barrier layer, the rate of moisture intrusion into the base 11 can be reduced. The barrier layer includes, for example, a metal or a metal oxide. The metals mentioned here include, for example, Al, Cu, Co, Mg, Si, Ti, V, Cr, Mn, Fe, Ni, Zn, Ga, Ge, Y, Zr, Mo, Ru, Pd, Ag, and Ba. , Pt, Au, and Ta. As the metal oxide, for example, a metal oxide containing one or more of the above metals can be used. More specifically, for example, at least one of Al ₂ O ₃ , CuO, CoO, SiO ₂ , Cr ₂ O ₃ , TiO ₂ , Ta ₂ O ₅ and ZrO ₂ can be used. Further, the barrier layer may include diamond-like carbon (DLC), diamond, or the like.

The average thickness of the barrier layer 15 is preferably 20 nm or more and 1000 nm or less, more preferably 50 nm or more and 1000 nm or less. The average thickness of the barrier layer 15 is determined in the same manner as the average thickness of the magnetic layer 13. However, the magnification of the TEM image is adjusted as appropriate depending on the thickness of the barrier layer 15.

(Modification 6)
In the above embodiment, a large number of holes 13A are formed on the surface 13S of the magnetic layer 13 by transferring a large number of protrusions 14A provided on the surface 14S of the back layer 14 to the surface 13S of the magnetic layer 13. Although the case where the holes are formed has been described, the method of forming the large number of holes 13A is not limited to this. For example, a large number of holes 13A may be formed on the surface 13S of the magnetic layer 13 by adjusting the type of solvent contained in the magnetic layer forming paint and the drying conditions of the magnetic layer forming paint.

(Modification 7)
The magnetic recording medium 10 according to the embodiment described above may be used in a library device. In this case, the library device may include a plurality of recording and reproducing devices 30 in the above-described embodiment.

EXAMPLES Hereinafter, the present disclosure will be specifically described with reference to Examples, but the present disclosure is not limited to these Examples.

In the following Examples and Comparative Examples, the average aspect ratio of the magnetic powder in the vertical direction, the average particle size of the magnetic powder, the average particle volume of the magnetic powder, the average thickness of the underlayer, the overall average thickness of the magnetic recording medium (tape average thickness), average thickness of the magnetic layer, coercive force Hc1, coercive force Hc2, ratio Hc2/Hc1, overall BET specific surface area of the magnetic recording medium, friction coefficient ratio μC(1000)/μC(5), and surface area of the magnetic layer. The arithmetic mean roughness (magnetic layer Ra) and magnetic layer PSD (≦0.5 μm) are values determined by the measurement method described in the above embodiment.

[Example 1]
A magnetic recording medium as Example 1 was obtained as follows.

<Preparation process of paint for forming magnetic layer>
A paint for forming a magnetic layer was prepared as follows. First, a first composition having the following composition was kneaded using an extruder. Next, the kneaded first composition and the second composition having the following composition were added to a stirring tank equipped with a disperser for preliminary mixing. Subsequently, the mixture was further mixed in a sand mill and filtered to prepare a coating material for forming a magnetic layer.

(First composition)
Each component and weight in the first composition are as follows.
・Barium ferrite (BaFe ₁₂ O ₁₉ ) particle powder (hexagonal plate shape, average aspect ratio 2.8, average particle size 20.3 nm, average particle volume 1950 nm ³ ): 100 parts by mass ・Vinyl chloride resin (cyclohexanone solution 30 parts by mass) Mass%): 40 parts by mass (including cyclohexanone solution)
(Polymerization degree 300, Mn=10000, contains OSO ₃ K=0.07 mmol/g and secondary OH=0.3 mmol/g as polar groups.)
・Aluminum oxide powder (α-Al ₂ O ₃ , average particle size 0.2 μm): 5 parts by mass ・Carbon black (manufactured by Tokai Carbon Co., Ltd., trade name: SEAST TA): 2 parts by mass

(Second composition)
The components and weights of the second composition are as follows.
・Vinyl chloride resin: 20 parts by mass (including cyclohexanone solution)
(Resin solution: resin content 30% by mass, cyclohexanone 70% by mass)
- Fatty acid ester: n-butyl stearate: 2 parts by mass - Methyl ethyl ketone: 121.3 parts by mass - Toluene: 121.3 parts by mass - Cyclohexanone: 60.7 parts by mass

To the magnetic layer forming paint prepared as described above, 4 parts by mass of polyisocyanate (trade name: Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) as a curing agent and 2 parts by mass of stearic acid as fatty acid were added.

<Preparation process of paint for base layer formation>
A paint for forming a base layer was prepared as follows. First, a third composition having the following composition was kneaded using an extruder. Next, the kneaded third composition and the fourth composition having the following composition were added to a stirring tank equipped with a disper for preliminary mixing. Subsequently, the mixture was further mixed in a sand mill and filtered to prepare a paint for forming a base layer.

(Third composition)
Each component and weight in the third composition are as follows.
・Acicular iron oxide powder (α-Fe ₂ O ₃ , average major axis length 0.15 μm): 100 parts by mass ・Vinyl chloride resin (resin solution: resin content 30% by mass, cyclohexanone 70% by mass): 55.6 Parts by mass: Carbon black (average particle size 20 nm): 10 parts by mass

(Fourth composition)
Each component and weight in the fourth composition are as follows.
- Polyurethane resin UR8200 (manufactured by Toyobo Co., Ltd.): 18.5 parts by mass - Fatty acid ester: n-butyl stearate: 2 parts by mass - Methyl ethyl ketone: 108.2 parts by mass - Toluene: 108.2 parts by mass - Cyclohexanone: 18. 5 parts by mass

To the base layer forming paint prepared as described above, 4 parts by mass of polyisocyanate (trade name: Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) as a curing agent and 2 parts by mass of stearic acid as fatty acid were added.

<Preparation process of paint for forming back layer>
A paint for forming a back layer was prepared as follows. A paint for forming a back layer was prepared by mixing the following raw materials in a stirring tank equipped with a disperser and filtering the mixture. - Small particle size carbon black powder (average particle size (D50) 20 nm): 90 parts by mass - Large particle size carbon black powder (average particle size (D50) 270 nm): 10 parts by weight - Polyester polyurethane (Japan Polyurethane) (Product name: N-2304): 100 parts by mass / Methyl ethyl ketone: 500 parts by mass / Toluene: 400 parts by mass / Cyclohexanone: 100 parts by mass

<Coating process>
Using the magnetic layer-forming paint and the base layer-forming paint prepared as described above, a film with an average thickness of 1.0 μm was coated on one main surface of a long polyester film with an average thickness of 4.0 μm, which is a non-magnetic support. An underlayer having a thickness of .1 μm and a magnetic layer having an average thickness of 80 nm were formed as follows. First, a base layer-forming paint was applied on one main surface of a polyester film and dried to form a base layer. Next, a magnetic layer-forming paint was applied onto the underlayer and dried to form a magnetic layer. In addition, when drying the paint for forming the magnetic layer, the magnetic powder was magnetically oriented in the thickness direction of the film using a solenoid coil. In addition, the drying conditions (drying temperature and drying time) of the paint for forming the magnetic layer were adjusted, and the coercive force Hc1 in the thickness direction (perpendicular direction) and the coercive force Hc2 in the longitudinal direction of the magnetic recording medium are shown in Table 2 below. set to the value. Subsequently, a back layer forming coating material was applied onto the other main surface of the polyester film and dried to form a back layer having an average thickness of 0.3 μm.

<Calendar process and transfer process>
Subsequently, a calender treatment was performed to smooth the surface of the magnetic layer. Next, the magnetic recording medium with the smoothed surface of the magnetic layer was wound up into a roll, and the magnetic recording medium in that state was subjected to a heat treatment at 60° C. for 10 hours. After rewinding the magnetic recording medium into a roll so that the end located on the inner circumferential side is located on the outer circumferential side, the magnetic recording medium is heated in that state at 60°C for 10 hours. The process was repeated. As a result, many protrusions on the surface of the back layer were transferred to the surface of the magnetic layer, and many holes were formed on the surface of the magnetic layer.

<Cutting process>
The magnetic recording medium obtained as described above was cut into 1/2 inch (12.65 mm) width pieces. As a result, the desired elongated magnetic recording medium (average thickness 5.6 μm) was obtained. This magnetic recording medium has a four-layer structure as shown in Table 2 below, has an overall average thickness (tape average thickness) of 5.6 μm, a number of servo tracks of 5, and a substrate (base film). The average thickness is 4.0 μm. Further, W is 2.9 μm, and L is 0.052 μm. The above configuration is referred to as media configuration 1. Furthermore, W represents the recording track width, and L represents the distance between magnetization reversals (bit length) of the portion recorded at the shortest wavelength. The magnetic layer Ra of the obtained magnetic recording medium was 1.9 nm, the magnetic layer PSD was 2.1 μm, and the half-width PW50 of an isolated waveform in the reproduced waveform was 175 nm.

[Example 2]
In the process of preparing a paint for forming a magnetic layer, the barium ferrite (BaFe ₁₂ O ₁₉ ) particles in the first composition have a powder average aspect ratio of 2.6, an average particle size of 18.6 nm, and an average particle volume of 1600 nm ³ . did. In addition, in the coating process, the average thickness of the magnetic layer was 60 nm, the coercive force Hc1 was 2920 Oe, and the coercive force Hc2 was 1920 Oe. Furthermore, the heating conditions were adjusted in the transfer process, and the BET specific surface area was set to 3.3 m ² /g, and the friction coefficient ratio μC(1000)/μC(5) was set to 1.3. A magnetic recording medium as Example 2 was obtained in the same manner as in Example 1 except for the above points. Note that the magnetic layer Ra of the obtained magnetic recording medium was 1.85 nm, and the magnetic layer PSD was 2.0 μm.

[Example 3]
In the process of preparing a paint for forming a magnetic layer, the barium ferrite (BaFe ₁₂ O ₁₉ ) particles in the first composition have a powder average aspect ratio of 3.0, an average particle size of 21.3 nm, and an average particle volume of 2100 nm ³ . did. Furthermore, the heating conditions in the transfer process were adjusted to give a BET specific surface area of 3.6 m ² /g. A magnetic recording medium as Example 3 was obtained in the same manner as in Example 1 except for the above points. Note that the magnetic layer Ra of the obtained magnetic recording medium was 1.9 nm, and the magnetic layer PSD was 2.1 μm.

[Example 4]
A magnetic recording medium as Example 4 was obtained in the same manner as in Example 1 except that the average thickness of the magnetic layer was 90 nm in the coating process. Note that the magnetic layer Ra of the obtained magnetic recording medium was 1.9 nm, and the magnetic layer PSD was 2.1 μm.

[Example 5]
In the process of preparing a paint for forming a magnetic layer, the barium ferrite (BaFe ₁₂ O ₁₉ ) particles in the first composition have a powder average aspect ratio of 2.9, an average particle size of 20.9 nm, and an average particle volume of 2050 nm ³ . did. Further, in the coating process, the coercive force Hc1 was set to 2980 Oe. A magnetic recording medium as Example 5 was obtained in the same manner as in Example 1 except for the above points. Note that the magnetic layer Ra of the obtained magnetic recording medium was 1.9 nm, and the magnetic layer PSD was 2.1 μm.

[Example 6]
In the process of preparing the paint for forming the magnetic layer, powder of ε iron oxide particles (spherical, average aspect ratio 1.3, average particle size 15.7 nm, particle volume 2050 nm ³ ) was used as the magnetic powder. Further, in the coating process, the coercive force Hc1 was set to 2850 Oe, and the coercive force Hc2 was set to 2020 Oe. Furthermore, the heating conditions in the transfer process were adjusted to give a BET specific surface area of 3.6 m ² /g. A magnetic recording medium as Example 6 was obtained in the same manner as in Example 1 except for the above points. Note that the magnetic layer Ra of the obtained magnetic recording medium was 2 nm, and the magnetic layer PSD was 2.1 μm.

[Example 7]
In the process of preparing the paint for forming the magnetic layer, cobalt ferrite powder (cubic shape, average aspect ratio 1.1, average particle size 12.6 nm, particle volume 2030 nm ³ ) was used as magnetic powder. Further, in the coating process, the coercive force Hc1 was set to 2800 Oe, and the coercive force Hc2 was set to 2020 Oe. Furthermore, the heating conditions in the transfer process were adjusted to give a BET specific surface area of 3.6 m ² /g. A magnetic recording medium as Example 7 was obtained in the same manner as in Example 1 except for the above points. Note that the magnetic layer Ra of the obtained magnetic recording medium was 2 nm, and the magnetic layer PSD was 2.1 μm.

[Example 8]
In the process of preparing the paint for forming the magnetic layer, the barium ferrite (BaFe ₁₂ O ₁₉ ) particles in the first composition had a powder average aspect ratio of 2.3, an average particle size of 17 nm, and an average particle volume of 1400 nm ³ . In addition, in the coating process, the average thickness of the magnetic layer was 60 nm, the coercive force Hc1 was 2550 Oe, and the coercive force Hc2 was 1820 Oe. Furthermore, the heating conditions in the transfer process were adjusted to give a BET specific surface area of 3.2 m ² /g. A magnetic recording medium as Example 8 was obtained in the same manner as in Example 1 except for the above points. Note that the magnetic layer Ra of the obtained magnetic recording medium was 1.8 nm, and the magnetic layer PSD was 1.9 μm.

[Example 9]
In the process of preparing the paint for forming the magnetic layer, the barium ferrite (BaFe ₁₂ O ₁₉ ) particles in the first composition had a powder average aspect ratio of 2.0, an average particle size of 15 nm, and an average particle volume of 1100 nm ³ . In addition, in the coating process, the average thickness of the magnetic layer was 60 nm, the coercive force Hc1 was 2500 Oe, and the coercive force Hc2 was 1840 Oe. Furthermore, the heating conditions in the transfer process were adjusted to give a BET specific surface area of 3.1 m ² /g. A magnetic recording medium as Example 9 was obtained in the same manner as in Example 1 except for the above points. The magnetic layer Ra of the obtained magnetic recording medium was 1.75 nm, the magnetic layer PSD was 1.8 μm, and the half-width PW50 of an isolated waveform in the reproduced waveform was 160 nm.

[Example 10]
A magnetic recording medium as Example 10 was obtained in the same manner as in Example 1 except that the media configuration was changed to 2 (Table 3). The magnetic layer Ra of the obtained magnetic recording medium was 1.9 nm, the magnetic layer PSD was 2.1 μm, and the half-width PW50 of an isolated waveform in the reproduced waveform was 175 nm.

[Example 11]
The media configuration was set to 3 (Table 3). In the process of preparing a paint for forming a magnetic layer, the barium ferrite (BaFe ₁₂ O ₁₉ ) particles in the first composition have a powder average aspect ratio of 2.6, an average particle size of 18.6 nm, and an average particle volume of 1600 nm ³ . did. In addition, in the coating process, the average thickness of the magnetic layer was 60 nm, the coercive force Hc1 was 2920 Oe, and the coercive force Hc2 was 1920 Oe. The tape average thickness was 5.2 μm. Furthermore, the heating conditions in the transfer process were adjusted to give a BET specific surface area of 3.3 m ² /g. A magnetic recording medium as Example 11 was obtained in the same manner as in Example 1 except for the above points. Note that the magnetic layer Ra of the obtained magnetic recording medium was 1.85 nm, and the magnetic layer PSD was 2.0 μm.

[Example 12]
The media configuration was set to 4 (Table 3). In the process of preparing the paint for forming the magnetic layer, the barium ferrite (BaFe ₁₂ O ₁₉ ) particles in the first composition had a powder average aspect ratio of 2.3, an average particle size of 17 nm, and an average particle volume of 1400 nm ³ . In addition, in the coating process, the average thickness of the magnetic layer was 60 nm, the coercive force Hc1 was 2550 Oe, and the coercive force Hc2 was 1820 Oe. The tape average thickness was 5.2 μm. Furthermore, the heating conditions in the transfer process were adjusted to give a BET specific surface area of 3.6 m ² /g. A magnetic recording medium as Example 12 was obtained in the same manner as in Example 1 except for the above points. Note that the magnetic layer Ra of the obtained magnetic recording medium was 1.8 nm, and the magnetic layer PSD was 1.9 μm.

[Example 13]
The media configuration was set to 5 (Table 3). In the process of preparing the paint for forming the magnetic layer, the barium ferrite (BaFe ₁₂ O ₁₉ ) particles in the first composition had a powder average aspect ratio of 2.3, an average particle size of 17 nm, and an average particle volume of 1400 nm ³ . In addition, in the coating process, the average thickness of the magnetic layer was 60 nm, the coercive force Hc1 was 2550 Oe, and the coercive force Hc2 was 1820 Oe. The average thickness of the tape was 4.5 μm. Furthermore, the heating conditions in the transfer process were adjusted to give a BET specific surface area of 3.3 m ² /g. A magnetic recording medium as Example 13 was obtained in the same manner as in Example 1 except for the above points. Note that the magnetic layer Ra of the obtained magnetic recording medium was 1.8 nm, and the magnetic layer PSD was 1.9 μm.

[Example 14]
The media configuration was set to 6 (Table 3). In the process of preparing the paint for forming the magnetic layer, the barium ferrite (BaFe ₁₂ O ₁₉ ) particles in the first composition had a powder average aspect ratio of 2.0, an average particle size of 15 nm, and an average particle volume of 1100 nm ³ . In addition, in the coating process, the average thickness of the magnetic layer was 60 nm, the coercive force Hc1 was 2500 Oe, and the coercive force Hc2 was 1840 Oe. The average thickness of the tape was 4.5 μm. Furthermore, the heating conditions in the transfer process were adjusted to give a BET specific surface area of 3.0 m ² /g. A magnetic recording medium as Example 14 was obtained in the same manner as in Example 1 except for the above points. Note that the magnetic layer Ra of the obtained magnetic recording medium was 1.75 nm, and the magnetic layer PSD was 1.8 μm.

[Example 15]
In the coating process, the average thickness of the magnetic layer was 90 nm, the coercive force Hc1 was 2990 Oe, and the coercive force Hc2 was 1500 Oe. A magnetic recording medium as Example 15 was obtained in the same manner as in Example 1 except for the above points. Note that the magnetic layer Ra of the obtained magnetic recording medium was 1.85 nm, and the magnetic layer PSD was 2.0 μm.

[Example 16]
In the coating process, the coercive force Hc1 was set to 2690 Oe, and the coercive force Hc2 was set to 2150 Oe. A magnetic recording medium as Example 16 was obtained in the same manner as in Example 1 except for the above points. Note that the magnetic layer Ra of the obtained magnetic recording medium was 1.85 nm, and the magnetic layer PSD was 2.0 μm.

[Example 17]
In the process of preparing the paint for forming the magnetic layer, powder of ε iron oxide particles (spherical, average aspect ratio 1.3, average particle size 15.7 nm, particle volume 2050 nm ³ ) was used as the magnetic powder. Further, in the coating process, the average thickness of the magnetic layer was 90 nm, the coercive force Hc1 was 2900 Oe, and the coercive force Hc2 was 1950 Oe. Furthermore, the heating conditions in the transfer process were adjusted to give a BET specific surface area of 3.3 m ² /g. A magnetic recording medium as Example 17 was obtained in the same manner as in Example 1 except for the above points. Note that the magnetic layer Ra of the obtained magnetic recording medium was 2 nm, and the magnetic layer PSD was 2.1 μm.

[Example 18]
By changing the calendering conditions, the BET specific surface area of the obtained magnetic recording medium was 2.5 m ² /g, the friction coefficient ratio μC(1000)/μC(5) was 1.8, and the magnetic layer Ra was 1. .6 nm, and the magnetic layer PSD was 1.7 μm.

[Example 19]
By changing the calendering conditions, the BET specific surface area of the obtained magnetic recording medium was 4.2 m ² /g, the friction coefficient ratio μC(1000)/μC(5) was 1.1, and the magnetic layer Ra was 2. .4 nm, and the magnetic layer PSD was 2.5 μm. Note that the half-width PW50 of the isolated waveform in the reproduced waveform was 175 nm.

[Comparative example 1]
In the process of preparing a paint for forming a magnetic layer, the barium ferrite (BaFe ₁₂ O ₁₉ ) particles in the first composition have a powder average aspect ratio of 3.5, an average particle size of 23.6 nm, and an average particle volume of 2450 nm ³ . did. In addition, in the coating process, the average thickness of the magnetic layer was 85 nm, and the coercive force Hc1 was 2820 Oe. Furthermore, the heating conditions were adjusted in the transfer step, so that the BET specific surface area was 3.7 m ² /g and the friction coefficient ratio μC(1000)/μC(5) was 1.1. A magnetic recording medium as Comparative Example 1 was obtained in the same manner as in Example 1 except for the above points. Note that the magnetic layer Ra of the obtained magnetic recording medium was 1.9 nm, and the magnetic layer PSD was 2.1 μm.

[Comparative example 2]
In the coating process, the average thickness of the magnetic layer was 100 nm. A magnetic recording medium as Comparative Example 2 was obtained in the same manner as in Example 1 except for the above points. Note that the magnetic layer Ra of the obtained magnetic recording medium was 1.9 nm, and the magnetic layer PSD was 2.1 μm.

[Comparative example 3]
In the coating process, the average thickness of the magnetic layer was 85 nm, the coercive force Hc1 was 2500 Oe, and the coercive force Hc2 was 2100 Oe. A magnetic recording medium as Comparative Example 3 was obtained in the same manner as in Example 1 except for the above points. Note that the magnetic layer Ra of the obtained magnetic recording medium was 1.9 nm, and the magnetic layer PSD was 2.1 μm.

[Comparative example 4]
In the process of preparing a paint for forming a magnetic layer, the barium ferrite (BaFe ₁₂ O ₁₉ ) particles in the first composition have a powder average aspect ratio of 3.0, an average particle size of 21.3 nm, and an average particle volume of 2090 nm ³ . did. Further, in the coating process, the coercive force Hc1 was set to 3100 Oe. A magnetic recording medium as Comparative Example 4 was obtained in the same manner as in Example 1 except for the above points. Note that the magnetic layer Ra of the obtained magnetic recording medium was 1.9 nm, and the magnetic layer PSD was 2.1 μm.

[Comparative example 5]
In the process of preparing the paint for forming the magnetic layer, powder of ε iron oxide particles (spherical, average aspect ratio 1.3, average particle size 15.7 nm, particle volume 2050 nm ³ ) was used as the magnetic powder. Further, in the coating process, the coercive force Hc1 was set to 2550 Oe, and the coercive force Hc2 was set to 2080 Oe. A magnetic recording medium as Comparative Example 5 was obtained in the same manner as in Example 1 except for the above points. Note that the magnetic layer Ra of the obtained magnetic recording medium was 1.9 nm, and the magnetic layer PSD was 2.1 μm.

[Comparative example 6]
In the process of preparing the paint for forming the magnetic layer, cobalt ferrite powder (cubic shape, average aspect ratio 1.1, average particle size 12.6 nm, particle volume 2030 nm ³ ) was used as magnetic powder. In addition, in the coating process, the coercive force Hc1 was set to 2450 Oe, and the coercive force Hc2 was set to 2080 Oe. A magnetic recording medium as Comparative Example 6 was obtained in the same manner as in Example 1 except for the above points. Note that the magnetic layer Ra of the obtained magnetic recording medium was 1.9 nm, and the magnetic layer PSD was 2.1 μm.

[Comparative Example 7]
By adjusting the additives in the magnetic layer, the magnetic layer Ra of the obtained magnetic recording medium was set to 2.55 nm, and the magnetic layer PSD was set to 3.2 μm. The BET specific surface area was 3.7 m ² /g, and the friction coefficient ratio μC(1000)/μC(5) was 1.1.

[Comparative example 8]
By adjusting the additives in the magnetic layer, the magnetic layer Ra of the obtained magnetic recording medium was set to 1.66 nm, and the magnetic layer PSD was set to 1.7 μm. The BET specific surface area was 3.4 m ² /g, and the friction coefficient ratio μC(1000)/μC(5) was 2.4.

[Comparative Example 9]
By changing the calendering conditions, the magnetic layer Ra of the obtained magnetic recording medium was set to 1.3 nm, and the magnetic layer PSD was set to 1.4 μm. The BET specific surface area was 2.4 m ² /g, and the friction coefficient ratio μC(1000)/μC(5) was 2.4.

[evaluation]
The magnetic recording media of Examples 1 to 19 and Comparative Examples 1 to 9 obtained as described above were evaluated as follows.

(C/N)
First, a reproduction signal of the magnetic recording medium was obtained using a loop tester (manufactured by Microphysics). The conditions for acquiring the reproduced signal are shown below.
Head: GMR Head speed: 2m/s
Playback signal: single recording frequency (10MHz)
Recording current: optimal recording current

Next, the reproduced signal was taken in by a spectrum analyzer, and the reproduced output value of 10 MHz and the average value of noise of 10 MHz±1 MHz were measured, and the difference between them was defined as C/N. The results are shown in Table 2 as relative values assuming that the C/N of Comparative Example 1 is 0 dB. Note that when the C/N is 1.5 dB or more, a medium that can withstand short wavelengths and narrow track densities can be realized.

Judgment as to whether running stability is good or bad is made using, for example, a recording/reproducing device as shown in FIG. First, record random data on the entire data area of the tape (full width and length of the tape) and confirm that it can be played back. Thereafter, a specific area on the tape (in this case, a position up to 20 m from the start of the data recording area on the tape) is reciprocated 20,000 times. After the round trip, the data in the entire data area (full width and length of the tape) is reproduced again to confirm whether the data can be read. If the data can be read out, it is defined as having good running stability. If the running stability is poor, problems such as the inability to read servo signals, high error rate, and inability to read all data occur.

Table 2 shows the magnetic properties and evaluation results of each magnetic recording medium in Examples 1 to 19 and Comparative Examples 1 to 9.

Table 3 shows the media configurations employed in the magnetic recording media of Examples 1 to 19 and Comparative Examples 1 to 9.

As shown in Tables 2 and 3, in Examples 1 to 19, the average thickness of the magnetic layer was 90 nm or less, the average aspect ratio of the magnetic powder was 1.0 or more and 3.0 or less, and The coercive force Hc1 is 3000 Oe or less, Hc2/Hc1 is 0.8 or less, and the total BET specific surface area of the magnetic recording medium in a state where the lubricant is removed is 2.5 m ² /g or more. Therefore, good electromagnetic conversion characteristics (C/N) can be ensured while maintaining good running stability of the magnetic recording medium. Therefore, a configuration advantageous for high-density recording can be realized.

In particular, in Examples 1 to 17 and 19, the entire BET specific surface area of the magnetic recording medium with the lubricant removed was set to 3.0 m ² /g or more, so the friction coefficient ratio (μB/μA) was 1. It became 4 or less. Therefore, compared to a case where the BET specific surface area is less than 3.0 m ² /g, the change in the coefficient of dynamic friction due to tension fluctuation during running is smaller, and the running of the magnetic recording medium can be made more stable.

In particular, in Examples 1, 3 to 7, 10, 15, 16, and 19, the entire BET specific surface area of the magnetic recording medium with the lubricant removed was set to 3.5 m ² /g or more, so the friction coefficient ratio (μB/μA) was 1.3 or less. Therefore, compared to the case where the BET specific surface area is less than 3.5 m ² /g, the change in the dynamic friction coefficient due to tension fluctuation during running was smaller, and the running of the magnetic recording medium was able to be made more stable. In particular, in Example 19, the entire BET specific surface area of the magnetic recording medium with the lubricant removed was set to 4.2 m ² /g, so the friction coefficient ratio (μB/μA) was 1.1 or less, The running of the magnetic recording medium could be made even more stable.

Furthermore, in Examples 1 to 19, the friction coefficient ratio (μC(1000)/μC(5)) is 1.0 or more and 1.8 or less, so changes in the dynamic friction coefficient due to multiple runs can be reduced, and magnetic recording It was possible to stabilize the running of the medium.

Further, in Examples 1 to 19, since the average particle size of the magnetic powder was 8 nm or more and 22 nm or less, it was possible to ensure good electromagnetic conversion characteristics (C/N).

Further, in Examples 1 to 19, the arithmetic mean roughness Ra of the surface of the magnetic layer was set to 2.5 nm or less, so that excellent electromagnetic conversion characteristics could be obtained. In Examples 1 to 19, the PSD up to a spatial wavelength of 5 μm was set to 2.5 μm or less, so it was possible to reduce the spacing between the recording/reproducing head and the tape-shaped magnetic recording medium during recording/reproducing. This makes it suitable for high recording density.

In Comparative Example 1, since the average aspect ratio of the magnetic powder exceeded 3.0, stacking of the magnetic tapes occurred and the electromagnetic conversion characteristics deteriorated.

In Comparative Example 2, the average thickness of the magnetic layer was large, and the electromagnetic conversion characteristics at short wavelengths deteriorated.

In Comparative Example 3, the degree of vertical alignment was low and the electromagnetic conversion characteristics deteriorated.

In Comparative Example 4, the perpendicular coercive force Hc1 was too large, so an unsaturated region occurred and the electromagnetic conversion characteristics deteriorated.

In Comparative Examples 5 and 6, the degree of vertical alignment was low and the electromagnetic conversion characteristics were deteriorated.

In Comparative Example 7, the electromagnetic conversion characteristics deteriorated due to deterioration of the surface properties of the magnetic layer.

In Comparative Example 8, although the electromagnetic conversion characteristics were improved, the increase in frictional force on the surface of the magnetic layer made it impossible for the magnetic recording medium to run.

In Comparative Example 9, although the electromagnetic conversion characteristics were improved, the magnetic recording medium became unable to run due to an increase in the frictional force on the surface of the magnetic layer.

Although the present disclosure has been specifically described above with reference to the embodiments and modifications thereof, the present disclosure is not limited to the above embodiments, etc., and various modifications are possible.

For example, the configurations, methods, processes, shapes, materials, numerical values, etc. mentioned in the above-mentioned embodiments and modifications thereof are merely examples, and the configurations, methods, processes, shapes, materials, numerical values, etc. that differ from these as necessary. etc. may also be used. Specifically, the magnetic recording medium of the present disclosure may include components other than the base, underlayer, magnetic layer, back layer, and barrier layer. Further, the chemical formulas of compounds, etc. are representative ones, and as long as they are general names of the same compound, they are not limited to the stated valence etc.

Further, the configurations, methods, processes, shapes, materials, numerical values, etc. of the above-described embodiments and their modifications can be combined with each other without departing from the gist of the present disclosure.

Furthermore, in the numerical ranges described in stages in this specification, the upper limit or lower limit of the numerical range of one stage may be replaced with the upper limit or lower limit of the numerical range of another stage. The materials exemplified in this specification can be used alone or in combination of two or more, unless otherwise specified.

As explained above, according to the magnetic recording medium as one embodiment of the present disclosure, it is possible to realize even higher density recording.
Note that the effects of the present disclosure are not limited to these, and may be any effects described in this specification. Further, the present technology can have the following configuration.
(1)
A tape-shaped magnetic recording medium,
a base containing polyester as a main component;
a magnetic layer provided on the base, containing a plurality of magnetic powders, and capable of recording data signals;
The average thickness of the magnetic recording medium is 5.6 μm or less,
The average thickness of the substrate is 4.2 μm or less,
The average thickness of the magnetic layer is 90 nm or less,
The average aspect ratio of the magnetic powder is 1.0 or more and 3.0 or less,
The magnetic recording medium has a coercive force in the vertical direction of 3000 Oe or less,
The ratio of the coercive force in the longitudinal direction of the magnetic recording medium to the coercive force in the vertical direction of the magnetic recording medium is 0.8 or less,
A magnetic recording medium, wherein the entire BET specific surface area of the magnetic recording medium in a state in which the lubricant is removed is 2.5 m ² /g or more.
(2)
The magnetic recording medium according to (1) above, wherein the entire BET specific surface area of the magnetic recording medium in a state in which the lubricant is removed is 3.0 m ² /g or more.
(3)
The magnetic recording medium according to (1) above, wherein the entire BET specific surface area of the magnetic recording medium in a state where the lubricant is removed is 3.5 m ² /g or more.
(4)
The magnetic recording medium according to (1) above, wherein the entire BET specific surface area of the magnetic recording medium in a state where the lubricant is removed is 4.0 m ² /g or more.
(5)
Dynamic friction coefficient μC(5) between the surface of the magnetic recording medium and the magnetic head at the fifth time from the start of running of the magnetic recording medium when the tension applied to the magnetic recording medium is 0.6N, and the magnetic Friction coefficient ratio μC(1000) between the dynamic friction coefficient μC(1000) between the surface of the magnetic recording medium and the magnetic head at the 1000th time from the start of running of the magnetic recording medium when the tension applied to the recording medium is 0.6N /μC(5) is 1.0 or more and 1.8 or less. The magnetic recording medium according to any one of (1) to (4) above.
(6)
The magnetic recording medium according to any one of (1) to (6) above, wherein the plurality of magnetic powders have an average particle diameter of 8 nm or more and 22 nm or less.
(7)
The magnetic recording medium according to any one of (1) to (6) above, wherein the plurality of magnetic powders have an average particle volume of 2300 nm ³ or less.
(8)
The arithmetic mean roughness Ra of the surface of the magnetic layer is 2.5 nm or less,
The magnetic recording medium according to any one of (1) to (7) above, wherein the PSD (Power Spectrum Density) up to a spatial wavelength of 5 μm is 2.5 μm or less.
(9)
The magnetic recording medium according to any one of (1) to (8) above, wherein the coercive force in the longitudinal direction is 2000 Oe or less.
(10)
The magnetic recording medium according to any one of (1) to (9) above, having an average thickness of 5.6 μm or less.
(11)
The magnetic recording medium according to any one of (1) to (10) above, wherein the base has an average thickness of 4.2 μm or less.
(12)
The magnetic powder is hexagonal ferrite containing at least one of Ba (barium) and Sr (strontium), ε iron oxide containing at least one of Al (aluminum) and Ga (gallium), or The magnetic recording medium according to any one of (1) to (11) above, including a spinel-type ferrite containing Co (cobalt).
(13)
The magnetic recording medium according to any one of (1) to (12) above, wherein the average thickness of the magnetic layer is 80 nm or less.
(14)
The magnetic recording medium according to any one of (1) to (13) above, wherein the average thickness of the magnetic layer is 60 nm or less.
(15)
When the coercive force in the vertical direction is Hc1 and the coercive force in the longitudinal direction is Hc2, Hc2/Hc1≦0.7 that satisfies the following conditional expression (1)... (1)
The magnetic recording medium according to any one of (1) to (14) above.
(16)
The magnetic recording medium according to any one of (1) to (15) above, wherein the coercive force in the perpendicular direction is 2200 Oe or more.
(17)
The magnetic layer has a plurality of servo bands each capable of recording a plurality of servo signals,
The magnetic recording medium according to any one of (1) to (16) above, wherein the ratio of the total area of the plurality of servo bands to the surface area of the magnetic layer is 4.0% or less.
(18)
The magnetic recording medium according to (17) above, wherein the number of the plurality of servo bands is 5 or more.
(19)
The magnetic recording medium according to (17) or (18) above, wherein the width of the servo band is 95 nm or less.
(20)
The magnetic layer can form a plurality of recording tracks,
The magnetic recording medium according to any one of (1) to (19) above, wherein the recording track has a width of 3.0 μm or less.
(21)
The magnetic recording medium according to any one of (1) to (20), wherein the magnetic layer is configured to be able to record data such that the minimum value of the distance between magnetization reversals is 48 nm or less.
(22)
a feeding section capable of sequentially feeding out tape-shaped magnetic recording media;
a winding unit capable of winding up the magnetic recording medium fed out from the feeding unit;
a magnetic head capable of writing information to and reading information from the magnetic recording medium while being in contact with the magnetic recording medium traveling from the sending section to the winding section; ,
The magnetic recording medium is
a base containing polyester as a main component;
a magnetic layer provided on the base, containing a plurality of magnetic powders, and capable of recording data signals;
The average thickness of the magnetic recording medium is 5.6 μm or less,
The average thickness of the substrate is 4.2 μm or less,
The average thickness of the magnetic layer is 90 nm or less,
The average aspect ratio of the magnetic powder is 1.0 or more and 3.0 or less,
The magnetic recording medium has a coercive force in the vertical direction of 3000 Oe or less,
The ratio of the coercive force in the longitudinal direction of the magnetic recording medium to the coercive force in the vertical direction of the magnetic recording medium is 0.8 or less,
The entire BET specific surface area of the magnetic recording medium in a state in which the lubricant is removed is 2.5 m ² /g or more. A magnetic recording and reproducing device.
(23)
a tape-shaped magnetic recording medium;
a casing that accommodates the magnetic recording medium;
The magnetic recording medium is
a base containing polyester as a main component;
a magnetic layer provided on the base, containing a plurality of magnetic powders, and capable of recording data signals;
The average thickness of the magnetic recording medium is 5.6 μm or less,
The average thickness of the substrate is 4.2 μm or less,
The average thickness of the magnetic layer is 90 nm or less,
The average aspect ratio of the magnetic powder is 1.0 or more and 3.0 or less,
The magnetic recording medium has a coercive force in the vertical direction of 3000 Oe or less,
The ratio of the coercive force in the longitudinal direction of the magnetic recording medium to the coercive force in the vertical direction of the magnetic recording medium is 0.8 or less,
A magnetic recording medium cartridge, wherein the entire BET specific surface area of the magnetic recording medium in a state in which the lubricant is removed is 2.5 m ² /g or more.

5... Recording track, 6... Servo signal recording pattern, 7... Stripe, 8... First stripe group, 9... Second stripe group, 10... Magnetic recording medium, 11... Substrate, 11A, 11B... Principal surface, 12 ...Underlayer, 13...Magnetic layer, 14...Back layer, 20, 20A...ε iron oxide particles, 21...Core part, 22...Shell part, 22a...First shell part, 22b...Second shell part, 30...Recording Playback device, 31... Spindle, 32... Reel, 33, 34... Drive device, 35... Guide roller, 36... Head unit, 37... Communication interface, 38... Control device, 41... Server, 42... Personal computer, 43... Network , 51... preprocessing section, 52... servo signal recording head, 53... servo signal reproducing head.

Claims (21)

A tape-shaped magnetic recording medium,
a base containing polyester as a main component;
a magnetic layer provided on the base, containing a plurality of magnetic powders, and capable of recording data signals;
The average thickness of the magnetic recording medium is 5.6 μm or less,
The average thickness of the substrate is 4.2 μm or less,
The average thickness of the magnetic layer is 90 nm or less,
The average aspect ratio of the magnetic powder is 1.0 or more and 3.0 or less,
The average particle volume of the magnetic powder is 2000 nm ³ or less,
The magnetic recording medium has a coercive force in the vertical direction of 3000 Oe or less,
The ratio of the coercive force in the longitudinal direction of the magnetic recording medium to the coercive force in the vertical direction of the magnetic recording medium is 0.75 or less,
the magnetic layer contains a lubricant,
The entire BET specific surface area of the magnetic recording medium in a state in which the lubricant is removed is 3.0 m ² /g or more ,
The coefficient of kinetic friction μA between the surface of the magnetic layer and the magnetic head when a tension of 0.4N is applied in the longitudinal direction of the magnetic recording medium, and A friction coefficient ratio (μB/μA) between the surface of the magnetic layer and the magnetic head in a state where the dynamic friction coefficient μB is 1.0 or more and 2.1 or less,
The arithmetic mean roughness Ra of the surface of the magnetic layer is 2.5 nm or less.
magnetic recording medium. The magnetic recording medium according to claim 1, wherein the entire BET specific surface area of the magnetic recording medium in a state in which the lubricant is removed is 4.0 m ² /g or more. The magnetic recording medium according to claim 1, wherein the plurality of magnetic powders have an average particle diameter of 8 nm or more and 22 nm or less. The magnetic recording medium according to claim 1, wherein the average particle volume of the magnetic powder is 1600 nm ³ or less. The average particle volume of the magnetic powder is 1400 nm ³ is below
The magnetic recording medium according to claim 1. The average aspect ratio of the magnetic powder is 1.0 or more and 2.8 or less.
The magnetic recording medium according to claim 1. The average aspect ratio of the magnetic powder is 1.0 or more and 2.0 or less.
The magnetic recording medium according to claim 1. The magnetic powder is hexagonal ferrite containing at least one of Ba (barium) and Sr (strontium), ε iron oxide containing at least one of Al (aluminum) and Ga (gallium), or The magnetic recording medium according to claim 1, comprising Co (cobalt)-containing spinel type ferrite. The magnetic recording medium according to claim 1, wherein the average thickness of the magnetic layer is 80 nm or less. The magnetic recording medium according to claim 1, wherein the average thickness of the magnetic layer is 60 nm or less. When the coercive force in the vertical direction is Hc1 and the coercive force in the longitudinal direction is Hc2, Hc2/Hc1≦0.7 that satisfies the following conditional expression (1)... (1)
The magnetic recording medium according to claim 1. The magnetic recording medium according to claim 1, wherein the coercive force in the perpendicular direction is 2200 Oe or more. The magnetic layer has a plurality of servo bands each capable of recording a plurality of servo signals,
The magnetic recording medium according to claim 1, wherein the ratio of the total area of the plurality of servo bands to the surface area of the magnetic layer is 4.0% or less. The magnetic recording medium according to claim 13, wherein the number of the plurality of servo bands is five or more. The magnetic recording medium according to claim 13 , wherein the width of the servo band is 95 μm or less. The magnetic layer can form a plurality of recording tracks,
The magnetic recording medium according to claim 1, wherein the recording track has a width of 3.0 μm or less. The magnetic recording medium according to claim 1, wherein the magnetic layer is configured to be able to record data such that the minimum value of the distance between magnetization reversals is 48 nm or less. The average thickness of the magnetic recording medium is 5.2 μm or less.
The magnetic recording medium according to claim 1. The average thickness of the magnetic recording medium is 5.0 μm or less.
The magnetic recording medium according to claim 1. a feeding section capable of sequentially feeding out tape-shaped magnetic recording media;
a winding unit capable of winding up the magnetic recording medium fed out from the feeding unit;
a magnetic head capable of writing information to and reading information from the magnetic recording medium while being in contact with the magnetic recording medium traveling from the sending section to the winding section; ,
The magnetic recording medium is
a base containing polyester as a main component;
a magnetic layer provided on the base, containing a plurality of magnetic powders, and capable of recording data signals;
The average thickness of the magnetic recording medium is 5.6 μm or less,
The average thickness of the substrate is 4.2 μm or less,
The average thickness of the magnetic layer is 90 nm or less,
The average aspect ratio of the magnetic powder is 1.0 or more and 3.0 or less,
The average particle volume of the magnetic powder is 2000 nm ³ or less,
The magnetic recording medium has a coercive force in the vertical direction of 3000 Oe or less,
The ratio of the coercive force in the longitudinal direction of the magnetic recording medium to the coercive force in the vertical direction of the magnetic recording medium is 0.75 or less,
the magnetic layer contains a lubricant,
The entire BET specific surface area of the magnetic recording medium in a state in which the lubricant is removed is 3.0 m ² /g or more ,
The coefficient of kinetic friction μA between the surface of the magnetic layer and the magnetic head when a tension of 0.4N is applied in the longitudinal direction of the magnetic recording medium, and A friction coefficient ratio (μB/μA) between the surface of the magnetic layer and the magnetic head in a state where the dynamic friction coefficient μB is 1.0 or more and 2.1 or less,
The arithmetic mean roughness Ra of the surface of the magnetic layer is 2.5 nm or less.
Magnetic recording and reproducing device. The magnetic recording medium according to any one of claims 1 to 19 ,
a casing for accommodating the magnetic recording medium ;
Magnetic recording media cartridge.

Images